European leaders will join Ukrainian President Volodymyr Zelenskyy to meet U.S. President Donald Trump in Washington as they look to strengthen his hand while Trump pushes Kyiv toward swiftly agreeing to a deal in the Ukraine conflict.

Trump is leaning on Zelenskyy to strike an agreement after he met Russian President Vladimir Putin in Alaska and emerged more aligned with Moscow on seeking a peace deal instead of a ceasefire first. Trump and Zelenskyy will meet on Monday.

"If peace is not going to be possible here and this is just going to continue on as a war, people will continue to die by the thousands ... we may unfortunately wind up there, but we don't want to wind up there," Secretary of State Marco Rubio said in an interview with CBS' "Face the Nation."

Trump on Sunday promised "BIG PROGRESS ON RUSSIA" in a social media post without specifying what this might be.

Following his Alaska meeting with Trump, Putin said on August 16 that Russia respects the U.S. government's position that it is necessary to bring the military conflict to a swift end.

"We also hope to resolve all issues through peaceful means," he said.

Top Trump officials hinted the fate of Ukraine's eastern Donbas region – which incorporates Donetsk and Luhansk and which is already mostly under Russian control – was on the line, while some sort of defensive pact was also on the table.

"We were able to win the following concession, that the United States could offer Article 5-like protection," Trump envoy Steve Witkoff told CNN's "State of the Union" on Sunday, suggesting this would be in lieu of Ukraine seeking NATO membership. He said it was "the first time we had ever heard the Russians agree to that."

Article 5 of NATO's founding treaty enshrines the principle of collective defense, the notion that an attack on a single member is considered an attack on them all.

Prior to his departure for Washington, Zelenskyy on Sunday met with European Commission President Ursula von der Leyen in Brussels, after which he said Ukraine regards joining the EU as part of its security guarantees.

Strong security guarantees are vital for both Ukraine and Europe, von der Leyen said at a joint press conference with the Ukrainian leader, adding that the EU welcomes Trump's statement that Washington is prepared to provide security assurances to Kyiv and will continue to advance Ukraine's accession into the bloc.

Emphasizing the EU's readiness to intensify pressure on Russia, von der Leyen said the bloc is working on a draft for its 19th package of sanctions against Moscow, set to be unveiled in early September.

German Chancellor Friedrich Merz, French President Emmanuel Macron and British Prime Minister Keir Starmer also hosted a meeting of allies on Sunday to bolster Zelenskyy's hand, hoping in particular to lock down robust security guarantees for Ukraine that would include a U.S. role.

They will travel to Washington along with von der Leyen, Finland's President Alexander Stubb and Italian Prime Minister Giorgia Meloni. In a joint statement issued on August 16, the leaders said they were ready to push for a trilateral summit between Zelenskyy, Trump and Putin.

(With input from agencies)