After Sunday’s bombshell decision not to seek re-election, Joe Biden still has six months left as the US president and commander-in-chief, and foreign leaders could be expected to write off the American president as a lame duck.

Around the world, heads of government and top diplomats had been preparing for a sea change in US policy under a potential Donald Trump administration, guided by his America First views that are broadly skeptical of Europe, unsympathetic toward Ukraine, hawkish on China and pro-Israel.

But by abandoning a losing campaign that seemed destined to throw the election to Trump, Biden may have a chance to pass on his legacy to a next Democratic administration – if his party can quickly regroup around a candidate that can make them competitive in November.

“I actually think the announcement puts [Biden] in a stronger position, because the likelihood of continuity of policy into a Democratic administration is more likely now,” said Kori Schake, the director of foreign and defense policy studies at the American Enterprise Institute, and a former national security council and state department official during the George W Bush administration.

Biden will be put to the test on Monday as Israel’s Benjamin Netanyahu flies to Washington to address a joint session of Congress and hold a series of high-stakes meetings at the White House that could influence whether he concludes a ceasefire deal with Hamas or contemplates a broader military campaign along the border with Lebanon. The Biden administration wants the ceasefire and has warned Netanyahu against escalating the conflict.

Last week’s Republican National Convention was attended by a number of European ambassadors seeking to remain close to the Trump campaign. But after Biden’s withdrawal, the momentum may swing back toward the centre.

“Foreign leaders were all angling to meet former President Trump and the people close to him; now they’ll be scrambling to meet the Democratic challengers and figure out who might be influential with them,” said Schake.

Netanyahu was already scheduled to hold meetings with vice-president Harris in Washington, said John Kirby, a spokesperson for the national security council, during a briefing last week. Netanyahu would probably also have lines of communication to the Trump campaign, said a European diplomat.

“I think [Netanyahu] has to balance a bit more what he hears in Washington from the two sides,” the diplomat said. “It’s now returned to being an open question again as to which way the elections will go.”

The US election campaign comes at a pivotal moment in global affairs, with major conflicts ongoing in Ukraine and in Gaza, both US parties warning of a growing great-power rivalry with China, and European allies unsettled by both a revanchist Russia and a potential America First policy under Trump that could see Washington turn its back on the continent.

“I think until today decision making in Jerusalem, Moscow, Beijing, or Tehran rested on the confident assumption that the next US president would be called Trump,” said Dr Constanze Stelzenmüller, director of the Center on the United States and Europe at the Brookings Institution.

Now that is not so clear, although much will depend on whether the Democrat’s successor campaign, under Harris or another candidate, can quickly get up to speed.

“Whether that changes now depends on the team the Democrats nominate – and how they do it. But I can see Biden deploying his experience and expertise in an elder statesman role,” Stelzenmüller said.

Views still vary and much will depend on the coming days. Dr Liana Fix, a fellow for Europe at the Council on Foreign Relations, said Biden himself would be seen as a “lame duck”, adding: “Foreign leaders will perceive him as on his way out: it will make little sense to try and advance any policy issues with him now.”

European leaders are likely to be frustrated to lose a Biden presidency that had largely led the way on the conflict in Ukraine, said Fix, while US adversaries could also seek to press Biden abroad amid the political tumult in the United States.

“The question is whether US adversaries such as Iran and Russia will try to test the strength and leadership of the US in this transition period, by stepping up escalation in Ukraine or through the Houthis, for example,” she said.

The Gaza war is another area where Biden’s influence has already been tested. Biden for a year had withheld a White House invitation for Netanyahu, whom he had hesitantly sought to restrain after the 7 October Hamas attack. Netanyahu was broadly seen as waiting out Biden in favour of the incoming Trump adminstration, which was seen as more amenable to an aggressive Israeli policy.

“I actually, honestly, I don’t think it makes him look any weaker, because he was already in such a terrible position,” said one senior European diplomat ahead of the Netanyahu visit.

Coming into this week, that person said, the two would probably discuss a potential deal to return Israeli hostages held in Gaza and conclude a ceasefire deal, on which Biden said the two sides have agreed on a “framework.”

They would also likely discuss Netanyahu’s threats of an operation in Lebanon, which would mark a significant escalation in the conflict.

Somewhat counterintutively, the next steps for Biden’s power abroad may depend heavily on how his protege and vice-president manages her campaign in the coming days and months.

Biden and other senior democrats have endorsed Harris, but that support is not unilateral, and others may seek the party’s nomination.

Meanwhile, foreign leaders will be watching closely.

“They’ve been reacting already with gratitude and praise on social media – but they will know better than to assume that a Harris nomination is a foregone conclusion,” Stelzenmüller said of foreign leaders. “Any Democrat who is nominated, and wins, is likely to be less of a visceral transatlanticist than Joe Biden.”