By ISABEL DEBRE Associated Press

Joe Biden’s withdrawal from the U.S. presidential race injects greater uncertainty into the world at a time when Western leaders are grappling with wars in Ukraine and Gaza, a more assertive China in Asia and the rise of the far right in Europe.

During a five-decade career in politics, Biden developed extensive personal relationships with multiple foreign leaders that none of the potential replacements on the Democratic ticket can match. After his announcement, messages of support and gratitude for his years of service poured in from near and far.

The scope of foreign policy challenges facing the next U.S. president makes clear how consequential what happens in Washington is for the rest of the planet. Here’s a look at some of them.

ISRAEL

With Vice President Kamala Harris being eyed as a potential replacement for Biden, Israelis on Sunday scrambled to understand what her candidacy would mean for their country as it confronts increasing global isolation over its military campaign against Hamas.

Israel’s left-wing Haaretz daily newspaper ran a story scrutinizing Harris’ record of support for Israel, pointing to her reputation as Biden’s “bad cop” who has vocally admonished Israel for its offensive in Gaza. In recent months, she has gone further than Biden in calling for a cease-fire, denouncing Israel’s invasion of Rafah and expressing horror over the civilian death toll in Gaza.

“With Biden leaving, Israel has lost perhaps the last Zionist president,” said Alon Pinkas, a former Israeli consul general in New York. “A new Democratic candidate will upend the dynamic.”

Biden’s staunch defense of Israel since Hamas’ Oct. 7 attack has its roots in his half-century of support for the country as a senator, vice president, then president. Israeli Defense Minister Yoav Gallant thanked Biden for his “unwavering support of Israel over the years.” Hamas has been designated as a terrorist organization by the United States, Canada and the European Union.

“Your steadfast backing, especially during the war, has been invaluable,” Gallant wrote on social media platform X.

Israeli President Isaac Herzog praised Biden as a “symbol of the unbreakable bond between our two peoples” and a “true ally of the Jewish people.” There was no immediate reaction from Prime Minister Benjamin Netanyahu, an ally of former President Donald Trump whose history of cordial relations with Biden has come under strain during the Israel-Hamas war.

UKRAINE

Any Democratic candidate would likely continue Biden’s legacy of staunch military support for Ukraine. But frustration with the Biden administration has grown in Ukraine and Europe over the slow pace of U.S. aid and restrictions on the use of Western weapons.

“Most Europeans realize that Ukraine is increasingly going to be their burden,” said Sudha David-Wilp, director of the Berlin office of the German Marshall Fund, a research institute. “Everyone is trying to get ready for all the possible outcomes.”

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Ukrainian President Volodymyr Zelenskyy said on X that he respected the “tough but strong decision” by Biden to drop out of the campaign, and he thanked Biden for his help “in preventing (Russian President Vladimir) Putin from occupying our country.”

Trump has promised to end Russia’s war on Ukraine in one day if he is elected — a prospect that has raised fears in Ukraine that Russia might be allowed to keep the territory it occupies.

Trump’s vice presidential pick, Ohio Sen. JD Vance, is among Congress’ most vocal opponents of U.S. aid for Ukraine and has further raised the stakes for Kyiv.

Russia, meanwhile, dismissed the importance of the race, insisting that no matter what happened, Moscow would press on in Ukraine.

“That’s it for Biden,” Dmitry Medvedev, deputy head of Russia’s Security council, said on the Telegram messaging app. “The goals of the special military operation will be achieved,” he added, using the Kremlin’s term for the war in Ukraine.

CHINA

In recent months, both Biden and Trump have tried to show voters who can best stand up to Beijing’s growing military strength and belligerence and protect U.S. businesses and workers from low-priced Chinese imports. Biden has hiked tariffs on electric vehicles from China, and Trump has promised to implement tariffs of 60% on all Chinese products.

Trump’s “America First” doctrine exacerbated tensions with Beijing. But disputes with the geopolitical rival and economic colossus over wars, trade, technology and security continued into Biden’s term.

China’s official reaction to the U.S. presidential race has been careful.

“The U.S. elections are U.S. internal politics. I have no comment on this,” said Foreign Ministry spokesperson Mao Ning.

The editor of the Communist Party-run Global Times newspaper, Hu Xijin, downplayed the impact of Biden’s withdrawal.

“Whoever becomes the presidential candidate of the Democratic Party may be the same,” he wrote on X.

IRAN

With Iran’s proxies across the Middle East increasingly entangled in the Israel-Hamas war, the U.S. confronts a region in disarray.

Yemen’s Iran-backed Houthis struck Tel Aviv for the first time last week, prompting retaliatory Israeli strikes inside war-torn Yemen. Simmering tensions and cross-border attacks between Lebanon’s Iran-backed Hezbollah militant group and the Israeli military have raised fears of an all-out regional conflagration.

Hamas, which also receives support from Iran, continues to fight Israel even nine months into a war that has killed 38,000 Palestinians and displaced over 80% of Gaza’s population.

The U.S. and its allies have accused Iran of expanding its nuclear program and enriching uranium to an unprecedented 60%, near-weapons-grade levels.

After then-President Trump in 2018 withdrew from Tehran’s landmark nuclear deal with world powers, Biden said he wanted to reverse his predecessor’s hawkish stance. But the Biden administration has maintained severe economic sanctions and overseen failed attempts to renegotiate the agreement.

The sudden death of Ebrahim Raisi — the supreme leader’s hard-line protege — in a helicopter crash vaulted a new reformist to the presidency in Iran, generating new opportunities and risks. Masoud Pezeshkian has said he wants to help Iran open up to the world but has maintained a defiant tone against the U.S.

During a briefing Monday, Nasser Kanaani, spokesperson for the Iranian Foreign Ministry, brushed off Biden’s withdrawal.

“To us, the coming and going of governments and persons on top of the U.S administration is not important on its own,” he said. “What can change the atmosphere of relations is a fundamental change in this (U.S.) hostile policy against the Islamic Republic of Iran.”

EUROPE AND NATO

Many Europeans were happy to see Trump go after his years of disparaging the European Union and undermining NATO. Trump’s seemingly dismissive attitude toward European allies in last month’s presidential debate did nothing to assuage those concerns.

Biden, on the other hand, has supported close American relations with bloc leaders.

That closeness was on stark display after Biden’s decision to bow out of the race. Polish Prime Minister Donald Tusk called his choice “probably the most difficult one in your life.” The newly installed British prime minister, Keir Starmer, said he respected Biden’s “decision based on what he believes is in the best interests of the American people.”

There was also an outpouring of affection from Irish Prime Minister Simon Harris, who called Biden a “proud American with an Irish soul.”

The question of whether NATO can maintain its momentum in supporting Ukraine and checking the ambitions of other authoritarian states hangs in the balance of this presidential election, analysts say.

“They don’t want to see Donald Trump as president. So there’s quite a bit of relief but also quite a bit of nervousness” about Biden’s decision to drop out, said Jeremy Shapiro, research director of the European Council on Foreign Relations. “Like many in the United States, but perhaps more so, they are really quite confused.”

MEXICO

The close relationship between Mexico and the U.S. has been marked in recent years by disagreements over trade, energy and climate change. Since President Andrés Manuel López Obrador took power in 2018, both countries have found common ground on issue of migration – with Mexico making it more difficult for migrants to cross its country to the U.S. border and the U.S. not pressing on other issues.

The López Obrador administration kept that policy while Trump was president and continued it into Biden’s term.

On Friday, Mexico’s president called Trump “a friend” and said he would write to him to warn him against pledging to close the border or blaming migrants for bringing drugs into the United States.

“I am going to prove to him that migrants don’t carry drugs to the United States,” he said, adding that “closing the border won’t solve anything, and anyway, it can’t be done.”

Associated Press writers Jill Lawless in London, Daria Litvinova in Tallinn, Estonia, and Josh Goodman in Miami contributed to this report.