British Prime Minister Keir Starmer rallied his European counterparts Sunday to shore up their borders and throw their full weight behind Ukraine as he announced outlines of a plan to end Russia’s war.

“Every nation must contribute to that in the best way that it can, bringing different capabilities and support to the table, but all taking responsibility to act, all stepping up their own share of the burden,” he said.

Starmer’s exhortation to 18 fellow leaders that they need to do the heavy lifting for their own security comes two days after U.S. backing of Ukraine appeared in jeopardy when President Donald Trump lashed out at Ukrainian President Volodymyr Zelenskyy and said he wasn’t grateful enough for America’s support.

The meeting had been overshadowed by the extraordinary scolding. Starmer used the opportunity as part of his broader effort to bridge the gap between Europe and the U.S. and also salvage what had seemed like the start of a peace process before Friday’s spat.

Starmer said he had worked with France and Ukraine on plan to end the war and that the group of leaders — mostly from Europe —had agreed on four things.

The steps toward peace would: keep aid flowing to Kyiv and maintain economic pressure on Russia to strengthen Ukraine’s hand; make sure Ukraine is at the bargaining table and any peace must ensure its sovereignty and security; continue to arm Ukraine to deter future invasion.

A ‘coalition of the willing’

Finally, he said they would develop a “coalition of the willing” to defend Ukraine and guarantee the peace.

“Not every nation will feel able to contribute but that can’t mean that we sit back,” he said. “Instead, those willing will intensify planning now with real urgency. The U.K. is prepared to back this with boots on the ground and planes in the air, together with others.”

Click to play video: 'Canadian volunteers in Ukraine more resolute after heated White House meeting'

He said any plan would require strong U.S. backing. He did not specify what that meant, though he told the BBC before the summit that there were “intense discussions” to get a security guarantee from the U.S.

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“If there is to be a deal, if there is to be a stopping of the fighting, then that agreement has to be defended, because the worst of all outcomes is that there is a temporary pause and then (Russian President Vladimir) Putin comes again,” Starmer said.

Starmer said he will later bring a more formal plan to the U.S. and work with Trump.

Two diplomatic steps forward, one back

Europe has been anxious since Trump initiated direct peace talks with Putin, who had been isolated by most Western leaders since invading Ukraine three years ago. The scramble to remain relevant and protect European interests as their once stalwart ally appeared to be cozying up to Putin was even more troubling when Trump called Zelenskyy a dictator and falsely said Ukraine started the war.

Meetings last week had provided some hope — until Zelenskyy’s trip to the White House.

Visits to the Oval Office by French President Emmanuel Macron, who had declared his visit a “turning point,” and Starmer were seen as steps in the right direction. The meetings were cordial and Trump even took a gentler tone toward Ukraine, though he would not commit to providing U.S. security guarantees and maintained Europe would need to provide peacekeeping troops.

Click to play video: 'Ukraine deal off after Trump’s public spat with Zelenskyy'

Within 12 hours of Starmer’s return from Washington, the talk of peace seemed to collapse as Vice President JD Vance berated Zelenskyy for challenging Trump’s assertions that Putin could be trusted.

During a press conference, Starmer rejected the suggestion that the U.S. was no longer a reliable ally.

“There are no two countries as closely aligned as our two countries and our defense, our security and intelligence is intertwined in a way no two other countries are, so it’s an important and reliable ally for us,” he said.

Starmer does not trust Putin

Starmer told the BBC before the summit that he does not trust Russian President Vladimir Putin but does trust Trump.

Italian Premier Giorgia Meloni said she was sorry for what happened with Zelenskyy in Washington. Meloni is both a strong Ukraine supporter and — as head of a far-right party —she is a natural ally of Trump. She was the only European leader to attend his inauguration.

She said told reporters following the meeting that Europe must remain focused on its common goals and that “dividing the West would be disastrous for everyone.”

“We need to work to reinforce our unity, and I think that Italy can play a role, not just in its own interest, but in everyone’s,” she said. “I don’t want to take any other scenario into consideration.”

Starmer hosted the meeting at Lancaster House, a 200-year-old mansion near Buckingham Palace, following his charm offensive with Macron to persuade Trump to put Ukraine at the center of negotiations and tilt his allegiances toward Europe.

Leaders from Germany, Denmark, Italy, Netherlands, Norway, Poland, Spain, Canada, Finland, Sweden, the Czech Republic and Romania were at the summit. The Turkish foreign minister, NATO secretary-general and the presidents of the European Commission and European Council were also in attendance.

Turning Ukraine into a ‘steel porcupine’

Starmer used sweeping terms to describe the challenge ahead, saying Europe was at a crossroads in its history and needed to step up to meet “once in a generation moment.”

European Commission president Ursula von der Leyen emerged from the meeting and said she would present a plan to “rearm Europe” to bolster the bloc’s security after a long period of under investment.

As for the future of war-torn Ukraine, von der Leyen said it needs security guarantees.

“We have to put Ukraine in a position of strength, so that it has the means to fortify itself and to protect itself,” von der Leyen said. “It’s basically turning Ukraine into a steel porcupine that is indigestible for potential invaders.”

Click to play video: 'Displaced Ukrainians reflect on ‘surreal’ 3 years of war'

Last week, Starmer pledged to boost military spending to 2.5% of gross domestic product by 2027. Other European nations may follow suit.

Czech Prime Minister Petr Fiala said Saturday that Europe faces a historic test and has to look after itself. He said European countries have to increase their arms spending to reach at least 3% of GDP.

“If we don’t increase our effort fast enough and let the aggressor dictate its conditions, we won’t end up well,” he said.

Starmer pledged to supply more arms to defend Ukraine, announcing that the U.K. will use 1.6 billion pounds (US$2 billion) in export financing to supply 5,000 air defense missiles.

Associated Press writers Jill Lawless in London, Colleen Barry in Milan, Karel Janicek in Prague and Samuel Petrequin contributed.