When Prime Minister Fumio Kishida of Japan stepped down on Wednesday, he became the latest in a growing line of unpopular leaders to cycle through a sclerotic political system that has faced growing frustration from the public.

Mr. Kishida, 67, announced at a news conference that he would not run in the governing Liberal Democratic Party’s leadership contest in September, the winner of which will go on to become the prime minister.

The Liberal Democrats have held an iron grip on Parliament for all but four years since 1955. But decades of scandals and its inability to tackle many of Japan’s deep-rooted challenges have spurred widespread voter dissatisfaction.

Mr. Kishida, a moderate party stalwart, was not popular even when he first took office in October 2021, and in recent months his approval ratings have plummeted to new lows.

But for all that, even though polls have revealed the Japanese public’s deep discontent with the governing party, it only rarely appears at the ballot box. Low voter turnout and weak political opposition in Japan have left the Liberal Democratic Party largely insulated from the pressure of potentially losing a general election.

Mr. Kishida said on Wednesday that he hoped his decision would enable the Liberal Democrats to make a big change.

“Government can only exist with the trust of the people, and I made my decision based on a strong desire to move political reform forward,” he said. “The most obvious first step to show that the Liberal Democratic Party is changing is for me to step down.”

But whether the governing party’s elite power brokers are finally ready to choose a candidate able and willing to bring any notable change — after years of resisting that pressure — is a huge question hanging over Japan in the next month.

In recent months, Mr. Kishida has seen his ratings slide in response to yet another scandal that emerged involving prominent lawmakers within the Liberal Democratic Party. His reputation has also soured over rising prices that have put pressure on households and Japan’s broader economy.

Political analysts said Mr. Kishida’s reputation suffered because he was viewed as a leader unable to offer bold solutions to problems such as Japan’s rapidly declining population, tepid economy and ballooning levels of debt. On the domestic front, Mr. Kishida has largely maintained the governing party’s longstanding economic policies, though they have failed to relieve the country’s stagnation.

Despite being in office for just less than three years, Mr. Kishida has become Japan’s eighth-longest-serving prime minister. Now, his resignation is reviving concerns within Japan that the country may return to the revolving door of prime ministers that has long characterized its political landscape.

Apart from former Prime Minister Shinzo Abe, who served longer than any other Japanese leader, from 2012 to 2020, Japan has seen a series of relatively short-lived prime ministers fail to implement dramatic policy changes and end up being forgotten soon after leaving office.

Government officials and security experts say the need for strong and unwavering leadership from Japan is particularly necessary today, in a moment of pronounced geopolitical uncertainty.

Japan, a crucial American ally, is facing not only an increasingly aggressive North Korea but also threats posed by China that include the country’s deepening economic and military ties with Russia and fears of a potential conflict with Taiwan.

During Mr. Kishida’s time in office, he worked closely with President Biden to enhance military and economic cooperation between the two longtime allies and with South Korea, with whom Japan’s relations have long been strained. He significantly bolstered Japan’s military defense, breaking with decades-long precedent on spending restraints.

The administrations of Mr. Abe and Mr. Kishida “were relatively stable, which was good for Japan’s diplomacy,” said Ken Jimbo, a professor of international politics and security at Keio University.

While Mr. Kishida ended up not having the energy needed to improve the ruling party’s reputation in Japan, he played to his strengths as a longtime foreign minister, Mr. Jimbo said.

The challenge for the next Liberal Democratic Party leader will be to deal with political uncertainty abroad — particularly within the United States — and to promote policies domestically that will help gain the backing of the Japanese people, Mr. Jimbo said.

“It’s not certain whether Japan will have another long-lasting administration,” he added.

Earlier this year, Mr. Kishida dissolved his own faction within the Liberal Democrats over a scandal involving campaign funds. The faction was found to have failed to officially report the equivalent of hundreds of thousands of dollars’ worth of political contributions. Other ruling-party factions failed to report even bigger sums.

The prime minister made various attempts to restore trust, including creating legislation to reform campaign finance rules. He also sought to dissolve the Japan branch of the fringe Unification Church after the group’s extensive ties to conservative Japanese politicians were revealed in the wake of Mr. Abe’s assassination two years ago.

Those moves did little to boost Mr. Kishida’s popularity. A poll last week by NHK, the public broadcaster, found that Mr. Kishida had an approval rating of just 25 percent, down from around 50 percent when he ascended to the role.

Mr. Kishida came into office in 2021, after a year in which voters had grown increasingly frustrated with the government’s handling of the pandemic and associated economic woes. He responded to public concerns by pledging to introduce “a new capitalism” and to encourage companies to distribute more of their profits to workers.

Mr. Kishida attempted to implement a number of policies aimed at drumming up domestic support, said Harumi Arima, an independent political analyst. Those included subsidies to families aimed at improving Japan’s low birthrate and several goals, such as doubling people’s income, that ultimately proved unrealistic.

Eventually, Mr. Kishida ended up “with no cards left to play,” Mr. Arima said. Ultimately, he will be remembered as a prime minister who “showed too much restraint” by hardly straying from party lines, but he did increase Japan’s defense budget “to better prepare it to take on a world full of tensions,” Mr. Arima said.

Mr. Kishida’s low approval ratings stemmed in part from policies Japan has implemented in recent years that have stoked a burst in inflation. The country’s central bank has stuck to rock-bottom interest rates and allowed prices to rise, but the newfound inflation has weighed on households and crippled consumer spending.

As Mr. Kishida’s popularity sank to new lows in recent months, the Liberal Democratic Party has been searching for a potential successor.

One prominent contender to lead Japan’s ruling party is Taro Kono, an outspoken Georgetown University-educated nonconformist whom Mr. Kishida beat in a runoff vote in 2021. The election between Mr. Kishida and Mr. Kono, Japan’s 61-year-old digital minister, was one of the most hotly contested in years.

At the time, public sentiment had swelled for Mr. Kono. But the party ultimately chose Mr. Kishida, in a move that traded lackluster public support for what it viewed as a safe pair of hands.

Other potential candidates to lead the Liberal Democratic Party include Toshimitsu Motegi, the party’s current secretary-general; Sanae Takaichi, a hard-line conservative who, if elected, would be the party’s first female leader; and Shigeru Ishiba, a prominent official who previously has run for the post four times.

Mr. Kishida said Wednesday that whomever the Liberal Democratic Party selected as its next leader would face “domestic and international difficulties that are truly severe.”

Heading into the upcoming election, he said, “the most important thing is to govern in a way that gains the sympathy of the people.”

The mob was growing, encircling the hotel near the northern English town of Rotherham where asylum seekers were living.

Abdulmoiz, an asylum seeker in his 20s from Sudan, said he watched from an upstairs window with other men trapped inside. All they could do was pray and wait, he said, as the men outside began attacking the building, throwing objects, breaking windows and chanting, “Get them out.” Some of the attackers tried to set fire to the building.

“People were in a panic,” said Abdulmoiz, who asked to be identified only by his first name to avoid jeopardizing his asylum claim, and who spoke just days after the attack through an interpreter. “If the people outside didn’t kill us,” he feared, “the smoke would.”

The assault two weekends ago came on one of the last big days of riots fueled by far-right agitators and an online disinformation campaign after a deadly knife attack on a children’s dance class in northwestern England. Much of the disinformation after that attack falsely claimed that the suspect — a teenager born in Britain — was an asylum seeker or that he had come to England illegally.

The police eventually managed to push back the Rotherham rioters, but not before some had broken into the building, further terrifying the residents, including Abdulmoiz. He has since moved to another hotel, in Birmingham, but he said the fear has barely abated.

The riots that shook Britain over more than a week have quieted, at least for now. The government has been working to charge and sentence rioters quickly, providing a clear warning to anyone who wanted to continue the violence that left dozens of police officers injured. Mosques, charities, lawyers that help asylum seekers, public buildings and businesses have been on high alert since the riots.

As of Monday, nearly 1,000 people had been arrested and nearly 550 had been charged, according to the National Police Chiefs’ Council. But the riots left a bitter aftertaste not just for asylum seekers, but also for others who felt they were once again the targets of abuse in a country where immigration has become a flashpoint.

Refugees and community organizers said those groups included immigrants and asylum seekers, but also Muslims, people who speak with a foreign accent and people who are not white.

In Rotherham, in the days right after the hotel attack, wives were asking husbands to accompany them to the grocery store, according to some residents and community leaders. Some parents kept their children at home even on sunny days. And people said they were afraid to go to the mosque to pray, afraid to go to the town center to shop and even afraid to go to the park to play soccer.

“Everybody is scared,” Yaqoob Adam, a refugee from Sudan, said late last week. “All the foreigners, all the refugees. And they haven’t done anything.”

Mr. Adam, who was born in Darfur, arrived in Britain in 2016 and has become a leader in the refugee community in Rotherham. An avid runner and athlete, he was celebrated in The Independent newspaper in 2018 as an outstanding member of British society. He organizes a soccer team and volunteers with several charities. (He also acted as an interpreter for Abdulmoiz.)

The riots have taken a toll on the community. Last week, Mr. Adam canceled a soccer game. Some of his regular players had lived in the hotel, a Holiday Inn Express, and they — along with other asylum seekers who had been staying there — had been moved to other locations after the attack. Other players were just too upset by the riots, he said.

He understands their lingering fears. And he shares them. How, he asked, crying, could people try to burn someone alive?

“We never came here to hurt anybody,” he said. “We came for a good life.”

There had been tensions in Rotherham before, he said, but nothing like this in recent years. On Wednesday night, he went to protect a nearby mosque, worried that it might be attacked during anti-immigrant protests planned that evening. They never materialized. And now he feels that he may not know what his neighbors actually think of him.

“I fled war in my country — genocide in my country — to come to England,” he said. But at least as of last week, he was too afraid to stay out past 10 p.m. “This is not freedom.”

The violence near Rotherham was aggravated by festering racial tensions stemming from memories of widespread sexual abuse that took place in the area from 1997 to 2013, residents say. At least 1,400 children were abused, an independent report released in 2014 said, while the authorities were accused of turning a blind eye to the problem. Most of the victims were white; the perpetrators were mostly of Pakistani heritage.

“The narrative was very much ‘us and them,’” said Abrar Javid, of the Rotherham Muslim Community Forum. He said that the report’s findings, and the far-right reaction, “radicalized a lot of the white communities.” He added, “It poisoned a lot of minds in Rotherham.”

For the asylum seekers at the Holiday Inn Express, their sense of marginalization was heightened by their isolation; the hotel was far from the center of Rotherham and far from mosques and halal shops, said Zaid Hussain, an imam at Masjid Uthman, a local mosque.

Activists who support immigration say housing asylum seekers at hotels can make them more vulnerable to attacks because the buildings are easily identifiable and relatively defenseless. At least one other hotel that had been used for years to house asylum seekers was attacked during the recent wave of violence, according to the BBC, and others have been the target of protests in the past.

“People living in these hotels are almost like sitting ducks,” said Kama Petruczenko, a senior policy analyst at the Refugee Council, a British nongovernmental organization.

Phil Turner, 72, who works with an organization called Stand Up to Racism Rotherham, said he led a counterdemonstration the day of the assault on the Holiday Inn Express and was trying to hold back what he called a “pogrom-style” attack on Muslims and migrants. The counterdemonstrators linked arms, chanting, “Refugees are welcome here,” but he said they were little match for the attackers.

“They were baying for blood,” he said. “It was a murderous mob.”

For Abdulmoiz, the violence felt frighteningly familiar. He said he had fled Sudan’s spiraling civil war before he was forced to join the fighting, like his three older brothers.

His escape took him through Chad, Libya and Tunisia, he said, then across the sea to Italy. He had no life jacket and feared drowning. He said the racism in Italy was so strong, he left for France and eventually boarded an inflatable boat to England.

Now, a week into his new life in Birmingham, Abdulmoiz said he was happier than he had been in Rotherham. Speaking at a coffee shop near his new hotel — this time in English with the occasional help of a translator app on his phone — he said that he no longer had to board a bus to get to a mosque. There is one just a 10-minute walk away.

And he likes that the city is diverse: There are more Sudanese, and other Africans, on the streets.

But he is still not sleeping well. What plagues him is the memory of the fire alarm that he said rang for hours as the riot raged at the hotel.

He can’t make it stop, he said: “It’s a sound I can’t forget.”

Rawan Sheikh Ahmad contributed research.

Since its surprise incursion into Russia more than a week ago, Ukraine has steadily gained ground, saying it advanced even deeper into Russian territory on Wednesday. It says it has captured hundreds of soldiers, as Russia has evacuated more than 130,000 people from nearby communities and declared a new state of emergency in one region.

And now Moscow has begun withdrawing some troops from Ukraine in an effort to repel Kyiv’s offensive into western Russia, according to U.S. and Ukrainian officials, an indication that the surprise attack is forcing Moscow to change its battle plans in Ukraine.

Taken collectively, Ukraine’s actions have deftly put Russia on the defensive, creating a new, if small, frontline in a war where Moscow has long had the upper hand. If Russia brings reinforcements in large numbers from other parts of the front, it could provide some relief to Ukrainian troops who are struggling to push back relentless Russian attacks, particularly in eastern Ukraine.

It is an edge that Ukraine appears intent on keeping, as its eyes, for now, holding the Russian territory it controls. President Volodymyr Zelensky discussed on Wednesday the possibility of establishing military administrations in areas seized by Ukrainian troops. The country’s interior minister, Ihor Klymenko, said Ukraine was creating a “buffer zone” in western Russia to protect border towns and villages. But it’s an advantage that may not translate into broader gains elsewhere — and one that may be hard to maintain.

Military analysts say Russia has so far responded by sending units that were not fighting in hot spots on the front, making it unclear whether Ukraine’s gambit would have the effect it desired on the overall battlefield. Russia has been careful not to pull troops out of eastern Ukraine, where its army has been steadily advancing in recent months.

As the incursion onto Russian soil enters its second week, the Ukrainian military will also face its own challenges, the analysts say. Capturing more land will become harder as Russian reinforcements arrive, while holding on to captured territory will expose stationary Ukrainian positions to potentially devastating airstrikes.

The Russian troop movements were reported by Dmytro Lykhovii, a spokesman for the Ukrainian Army, who told the Ukrainian news media on Tuesday that Russia had moved some units from the southern Ukrainian regions of Zaporizhzhia and Dnipro to other areas of the fighting, including the Kursk region.

In Washington, U.S. officials said on Wednesday that Russia had withdrawn some infantry units from Ukraine and was sending them to Kursk to help defend against the Ukrainian offensive. They would not say how many troops or where they coming from.

But the officials said they had not yet seen the Kremlin divert armored battalions and other combat power that the United States believes Russia would need to repel the incursion.

There is little sign that Moscow has redeployed troops from the Donetsk region of eastern Ukraine, which Moscow hopes to fully capture and where it has been on the offensive for months. Instead, the Russian Army appears to have sent in reinforcements drawn mainly from less combat-ready units based in northern Russia and Ukraine, military experts say.

“The Russian strategy is to avoid drawing from units in the Donetsk direction as much as possible,” said Serhii Kuzan, the chairman of the Ukrainian Security and Cooperation Center, an independent research group. “The Russians are reluctant to do this, because it would jeopardize all the gains of their summer offensive campaign.”

The Institute for the Study of War, a Washington-based organization, said that the Russian authorities “appear to be largely relying on Russian conscripts, and elements of some regular and irregular military units pulled from less critical sectors of the frontline to address the ongoing Ukrainian incursion.”

Lithuania’s defense minister, Laurynas Kasciunas, said on Tuesday that Russia was moving troops from its Baltic enclave of Kaliningrad to Kursk. Mr. Kasciunas was visiting President Volodymyr Zelensky in Kyiv.

Ukrainian military officials said that Russian assaults in the Donetsk region had continued unabated over the past week, despite the new Ukrainian offensive. Russian troops have continued to slowly advance in or toward the frontline towns of Chasiv Yar, Niu York, Pokrovsk and Toretsk, they say.

Oleksandr Bordiian, a spokesman for the 32nd Separate Mechanize Brigade, which is fighting near Toretsk, told the Ukrainian news media on Tuesday that Ukraine’s attacks in the Kursk region “have not yet had any impact on the density of assaults and shelling in our direction.” A medic fighting in another brigade near Toretsk also said on Wednesday that there had been no changes on that part of the front.

On Wednesday, Gen. Oleksandr Syrsky, Ukraine’s top commander, told Mr. Zelensky that Ukrainian troops had advanced up to two kilometers, about 1.2 miles, in the Kursk region since the beginning of the day. He also said that more than 100 Russian soldiers had been captured during the day. His claims could not be independently verified.

Military analysts say that Kyiv will need to expand or hold onto its gains in western Russia long enough to compel Moscow to divert significant forces from the battlefield in Ukraine.

After quick successes in the early days of the offensive, Ukraine’s advance in the Kursk region appears to have slowed, according to maps of the battlefield compiled by independent analysts. Ukrainian troops are now attacking to the north and south of the bulge they have carved out in Russian territory, but are facing more Russian resistance, the maps show.

Emil Kastehelmi, an analyst with the Finland-based Black Bird Group, which scrutinizes footage from the battlefield, said on Tuesday evening that an attack by Ukrainian troops on Giri, a village southeast from the initial Ukrainian drive and about eight miles from the Ukrainian border, had likely been repelled. “They suffered significant losses and likely had to retreat,” Mr. Kastehelmi wrote on social media.

The Ukrainian raids appear to have a strategy of probing and destabilizing Russian defenses. After several days of Ukrainian attacks on the Belgorod region, which borders Kursk, the regional governor, Vyacheslav Gladkov, declared a state of emergency on Wednesday.

Whether Ukraine can continue to conduct these raids depends on the number of troops it can commit to the fight. Its forces are stretched thin, and Kyiv has already sent experienced units, pulled from the front in eastern Ukraine, into the offensive.

France’s defense ministry said on Monday that Kyiv’s forces “appear to have reduced the pace of their initial advance, but are consolidating their positions” in captured territory.

But holding on to a position that can be attacked from multiple sides will prove difficult, analysts say. Mr. Kuzan, of the Ukrainian Security and Cooperation Center, also noted the vulnerability of fixed Ukrainian position to Russian airstrikes. Such a dynamic, he said, “immediately invites the use of aviation, guided bombs and ballistic missiles.”

Olha Konovalova contributed research, and Eric Schmitt contributed reporting.

Thailand’s Constitutional Court ousted Prime Minister Srettha Thavisin from office on Wednesday, throwing the country into fresh political turmoil just days after the court dissolved the country’s main opposition party.

In a 5-4 verdict, the court ruled that Mr. Srettha, who took office almost a year ago, violated ethics standards after he appointed to his cabinet a member previously convicted of attempted bribery.

Mr. Srettha was seen as a figurehead, closely allied with Thaksin Shinawatra, a populist former prime minister who has long sought to influence the country’s politics even after he was ousted and exiled in a 2006 coup.

The court’s decision is likely to intensify the disillusionment of many Thais, who see the case as the latest proof of intervention by an unelected establishment that is quashing the people’s will. Last week, the same court ordered the disbandment of the Move Forward Party, a progressive party that won last year’s election but was blocked from forming a government.

The constant upheaval in politics has diminished the government’s ability to address pressing issues such as reviving the country’s ailing, tourism-dependent economy.

But this dismissal is unlikely to galvanize angry protests. Mr. Srettha, a mild-mannered 62-year-old billionaire tycoon, was not a popular leader. He was installed only because a military-backed Senate prevented Pita Limjaroenrat, Move Forward’s former leader, from becoming premier. During his short term in office, Mr. Srettha was criticized for traveling abroad frequently with few results to show for it. He has said those trips were necessary to stimulate tourism and foreign investment.

On Wednesday, Mr. Srettha told reporters that he accepted the verdict. “This chapter has ended as the Constitutional Court has decided,” he said outside his office.

Phumtham Wechayachai, a deputy to Mr. Srettha, will be the caretaker prime minister, according to Wissanu Krea-ngam, an adviser to Mr. Srettha.

The case against Mr. Srettha stemmed from his appointment of Pichit Chuenban, a lawyer and former fixer of Mr. Thaksin, to the prime minister’s office in May. Mr. Pichit was sentenced in 2008 to six months in prison for attempted bribery.

His appointment prompted a petition filed by 40 military-appointed senators calling for Mr. Srettha to be removed from office for violating the Constitution. Even though Mr. Pichit eventually stepped down, the court continued to pursue the case.

The ruling on Wednesday stunned many political analysts, who had expected Mr. Srettha to survive. The court had demonstrated earlier that it was divided, voting 6-3 to accept the petition and then allowing Mr. Srettha to stay on the job while it deliberated the case.

Wednesday’s ruling also served as a warning to the ambitions of Mr. Thaksin, a former prime minister and long a foil to Thailand’s royalist-military establishment. The ruling was the latest sign of a crack in the grand bargain Mr. Thaksin is thought to have cut with the royalist-military establishment. That deal allowed him to return to Thailand after years in exile and essentially avoid jail time.

But as Mr. Thaksin signaled he had higher political ambitions, Thailand’s old guard moved to show that it held the upper hand in that uneasy partnership. In June, Mr. Thaksin was charged with violating the country’s harsh royal defamation law. And now, his ally, Mr. Srettha, has been removed from office.

Critics say the ruling also served as a reminder of how the establishment has relied on institutions like the courts to do its bidding and demonstrate that elections in Thailand are a farce.

The next prime minister has to be chosen by Thailand’s Parliament. But it can only select from candidates who ran in last year’s election. Among the contenders, analysts say, are Anutin Charnvirakul, a deputy prime minister, and Paetongtarn Shinawatra, Mr. Thaksin’s youngest daughter.

Mr. Pita, the former Move Forward leader, is not eligible. When the court disbanded his party last week, it also banned him from politics for 10 years.

Muktita Suhartono contributed reporting.

Two military bases in Germany were put under heightened security on Wednesday after contaminants were found in the water supply of barracks at one site — the result of possible sabotage, the military said — and an intruder attempted to forcibly enter a NATO base in the country.

A hole was found early Wednesday in the fence near the barracks’ drinking water supply at the German Army base in Cologne-Wahn, in the state of North Rhine-Westphalia, according to an official release by the military. The discovery led to the temporary lockdown while the supply was tested. The water showed “unusual values,” the military said, but did not specify of what.

Later on Wednesday, NATO officials reported that a person had tried to enter by force at the alliance’s base in Geilenkirchen, near the border with the Netherlands. It was put on a heightened alert but not locked down, according to a spokesman. The water there was tested and found to be normal, he added.

Col. Arne Collatz, a spokesman for the German defense ministry, told reporters it did not immediately appear that the two episodes were related.

The German base is near Cologne’s airport and houses air force and medical facilities, as well as other elements of the Bundeswehr, or German military. Approximately 4,000 soldiers and 1,500 civilians are employed at the site.

Colonel Collatz did not reveal what, if any, effect the possible contaminant could have had on people who came into contact with it at the base. But a statement issued on Wednesday by the military’s territorial leadership command said it “wishes all members of the armed forces who had come to harm during the incident a speedy and complete recovery.”

The United States opened new peace talks on Wednesday that aim to stop Sudan’s catastrophic civil war, driven by a growing sense of urgency that the country’s deepening famine, which threatens millions of lives, could become the world’s worst in decades.

But Sudan’s military, one of the war’s two main belligerents, did not send a delegation to the negotiations in Switzerland, stymying hopes of a quick cease-fire in a destructive fight between the forces of two rival generals that has now lasted 16 months.

Famine was officially declared earlier this month in Sudan’s western Darfur region, and other areas are expected to follow. By one estimate as many as 2.5 million Sudanese could die from hunger by the end of September.

Appalled at the scale of the war-induced calamity in Africa’s third largest country, American officials say the peace drive is necessary, even if chances of a breakthrough seem slim.

Lt. Gen. Mohamed Hamdan, the paramilitary leader whose Rapid Support Forces are fighting the military, sent a delegation to the talks. But after a drone strike appeared to target the army leadership at a parade in eastern Sudan on July 31, the military chief, Gen. Abdel Fattah al-Burhan, spurned the meeting.

“We will not retreat, we will not surrender and we will not negotiate,” General al-Burhan told troops.

However, the United Arab Emirates, which has been accused of arming the R.S.F., did send a representative to the talks in Geneva, drawing criticism from some Sudanese commentators who said the Emirates should not have been invited.

The Emirates, which denies backing the R.S.F., has observer status at the talks, as does Egypt, long a political backer of Sudan’s military.

The Switzerland meeting picks up from earlier talks in Jeddah, Saudi Arabia, that failed to stop the fighting and ultimately stalled after the Sudanese army also boycotted them. Even before the talks started on Wednesday, however, American officials sought to temper expectations.

Tom Perriello, the U.S. envoy to Sudan, said in an interview before the talks began that his goal is to broker a cease-fire and to strike a deal for full humanitarian access across Sudan, where more than 10 million people have been forced from their homes and tens of thousands are estimated to have died.

If the military stays away, American officials hope to pressure its leaders to return to the table and also to draw global attention to a ballooning humanitarian crisis in which aid remains chronically underfunded.

“We need to start pivoting to a different set of solutions if we are to prevent a couple of million people from starving,” Mr. Perriello said.

The United Nations has received just one-third of the $2.7 billion it requested for Sudan, where people are dying because aid groups lack money, said Mohamed Refaat, country director with the U.N.’s International Organization for Migration.

“We see people who are dying, and who we have access to, who we can’t do anything for,” Mr. Refaat said in a video call with reporters from the de facto capital, Port Sudan, where all government functions have been moved since Khartoum was destroyed by fighting.

Previous peace efforts stalled after the Sudanese military insisted that the R.S.F. first drop its guns and abandon most of the territorial gains it has made since April 2023, a position the military has maintained in recent weeks.

“Military operations will not stop without the withdrawal of every last militiaman from the cities and villages they have plundered and colonized,” General al-Burhan said in a statement on Tuesday.

But American officials began to also see Saudi Arabia, their partner in peace talks, as part of the problem, according to two officials who spoke on the condition of anonymity to discuss sensitive diplomacy.

Saudi officials were doing little to encourage talks to resume in Jeddah, and seemed to relish the growing tension between the United States and Saudi Arabia’s own rival, the United Arab Emirates, over the Emiratis’ continued military support of the R.S.F., the two officials said.

In Geneva, Saudi officials are no longer leading the mediation and are instead listed as “co-hosts” alongside Switzerland.

American officials insist the talks will focus narrowly on a cease-fire and humanitarian access. Still, many in Sudanese civil society fear the talks could pave the way for a power-sharing deal that would hand Sudan back to the warring generals whose feud is destroying the country, instead of leading to the democratic transition many once hoped for.

The talks carry risk for the United States, too. Sudanese and even former American officials said the Biden administration’s flawed diplomacy in 2022 set the stage for the outbreak of war in 2023.

“Well-intentioned but counterproductive diplomatic efforts” by the United States and others “at best, failed to prevent the war and at worst contributed to its outbreak,” Payton Knopf, a former state department official who participated in some of those efforts, wrote this week.

Some Sudanese commentators have called the Geneva talks a “now or never” opportunity, noting that the chief organizer, Mr. Perriello, could be replaced, depending on the outcome of the presidential election in the United States.

Mr. Perriello still hoped he might persuade the Sudanese military to turn up. American mediators “are still waiting,” he wrote on X on Tuesday night. “The world is watching.”

Nick Cumming-Bruce contributed reporting from Geneva.

A European arrest warrant was issued for a Ukrainian man suspected of involvement in blowing up the Nord Stream pipeline nearly two years ago, Polish prosecutors said on Wednesday.

The sabotage in September 2022 of the Nord Stream pipelines that carried Russian gas to Europe has become one of the central mysteries of the war in Ukraine, prompting extensive finger-pointing and guesswork. But until Wednesday, there were very few answers.

The Polish prosecutors office said it had received the warrant, issued by Germany, in June for a suspect who was living in Poland at the time. The suspect — identified only as Volodymyr Z., in keeping with German privacy laws — left the country before Polish authorities could detain him, according to Anna Adamiak, a spokeswoman for the prosecutor’s office in Warsaw.

The German federal prosecutor’s office declined to comment on the warrant, whose existence was first reported by a trio of German news outlets.

The warrant marks the first significant development toward potentially solving who was behind an act of sabotage that has sown political distrust among Western allies and raised the geopolitical stakes in Europe’s Baltic region.

The sabotage was first detected on Sept. 26 when a vast swirl of bubbles appeared on the surface of the Baltic Sea in international waters between Denmark and Sweden.

There was initial speculation that Russia was behind the explosions, but to some that made little sense — the Russians were deeply invested in both major lines of the pipeline, known as Nord Stream I and Nord Stream II.

Reports that a pro-Ukrainian group could have been behind the sabotage first emerged last year. That raised concerns in Berlin and Washington that supporting Ukraine could become more complicated. Germany is the European Union’s leading contributor of weapons to Ukraine.

U.S. officials said at the time that they had no evidence that the attack was done at the direction of the Ukrainian government, and Kyiv has flatly denied any responsibility.

Sweden and Denmark had both opened investigations into the blasts, but closed them earlier this year.

The German authorities, however, continued their investigation into the explosions, which rendered three of the four strands that make up Nord Stream 1 and 2 pipelines inoperable. Even before the blasts, though, Russia had severely curtailed the amount of natural gas it was sending to Germany via Nord Stream 1, citing problems with a turbine that had been sent to Canada for repairs. Nord Stream 2 had never come online.

Experts have said that divers could have been responsible for planting the explosives on the subsea pipes, and German news reports identified Volodymyr Z. as a professional diver. When the Süddeutsche Zeitung newspaper reached a man who identified himself by that name by telephone, he denied having any involvement with the attacks or knowing about the warrant.

A person briefed on the matter confirmed that German prosecutors had issued a warrant for a Ukrainian diver believed to be a member of the team that planted explosives on the pipelines. The diver was living in Poland but was able to escape before being apprehended, according to the person, who spoke on condition of anonymity in order to discuss an ongoing investigation.

The Süddeutsche, along with the Die Zeit newspaper and the German public broadcaster ARD, reported that the German authorities had tracked down the suspect after a speed camera recorded a van with Ukrainian license plates on the northeastern German island of Rügen on Sept. 8, 2022.

One of the passengers in the van was the suspect sought by German prosecutors, according to the German media outlets. The suspect lived in a suburb of Warsaw and worked as an instructor for a diving school in Kyiv, the media outlets reported.

Anatol Magdziarz contributed reporting from Warsaw.