Ukraine would receive security guarantees similar to those provided in Article 5 of the Nato treaty under a proposed peace deal discussed in Berlin, a US official told reporters on Monday.

Officials, speaking to reporters on a conference call after two days of US peace talks with Ukrainian and European officials, said those guarantees would not be on the table forever, as US President Donald Trump presses for an end to the war sparked by Russia's 2014 expanded invasion of Ukraine.

One official said Russia was open to Ukraine joining the European Union and that Trump wanted to prevent Russia from moving further west.

Article 5 is considered the cornerstone of the Nato defense alliance's founding treaty. It stipulates that an attack against one member of the group is considered an attack against them all. Ukraine is not a member of Nato.

It was not clear how far the United States would go in providing such security guarantees to Ukraine. The talks in Berlin were led on the US side by Trump envoys Steve Witkoff and Jared Kushner, the president's son-in-law.

The officials said they had reached agreement on 90 per cent of the issues involved. One said long-standing territorial issues remain but that "we've got multiple different solutions to bridge the gap that we are suggesting to them."

Ukraine has said previously it would not cede territory to Russia. The officials said the territorial issues would be worked out between the two warring parties.

Witkoff and Kushner planned to attend a dinner on Monday night in Berlin with the other negotiators and Trump was expected to call into the event, the officials said.

Working groups are expected to meet in the United States during the coming weekend, possibly in Miami, one of the officials said.

"I think you're going to hear that we have moved considerably closer in narrowing the issues between the Ukrainians and the Russians. That's clear," the official said.

The official said a working group came up with a three-page draft on territory issues and Zelensky is expected to discuss it with his team, and the US side will eventually discuss the topic with the Russians.

The officials described the security guarantees as "Article 5 like" with categories such as oversight and deconfliction.