Russia launched an overnight drone attack on Kyiv, Vitali Klitschko, mayor of the Ukrainian capital said early on Monday.

Klitschko, in a post on the Telegram messaging app, said that Ukrainian air defence units were trying to repel the attack.

Reuters' witnesses heard blasts in parts of the city in what sounded like air defence systems in operation.

Russia will seek guarantees that NATO countries will exclude Ukraine from membership and Ukraine will remain neutral in any peace deal, a Russian deputy foreign minister said in remarks published on Monday.

"We will demand that ironclad security guarantees become part of this agreement," Deputy Foreign Minister Alexander Grushko told the Russian media outlet Izvestia.

"Part of these guarantees should be the neutral status of Ukraine, the refusal of NATO countries to accept it into the alliance."

Lithuania on Sunday backed an EU proposal to pledge up to 40 billion euros ($43.5 billion) in military aid for Ukraine this year and said a similar amount would also be needed in future years to deter any future Russian attack.

"If we can sustain this amount ... for a longer period of time, that would be the amount that would allow Ukrainians to keep their armed forces at current strength," Lithuanian Foreign Minister Kestutis Budrys told Reuters on Sunday.

Budrys spoke on the eve of a meeting of EU foreign ministers in Brussels that will discuss the proposal, put forward by the bloc's diplomatic service, headed by former Estonian Prime Minister Kaja Kallas.

The meeting comes at a time of uncertainty about the outcome of U.S. negotiations with Russia, the future of U.S. assistance to Ukraine and Washington's commitment to European security.

EU diplomats suggested doubling military aid to Ukraine to as much as 40 billion euros, according to a document seen by Reuters on Friday.

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President Trump, who said he was willing to talk to the Russian leader by phone, called Mr Putin's statement "very promising" and said he hoped Moscow would "do the right thing".

But, he added: “Now we’re going to see whether or not Russia is there, and if they’re not, it’ll be a very disappointing moment for the world.”

He said Steve Witkoff, his special envoy, was engaged in serious talks with the Russians in Moscow on the US proposal, which Kyiv has already agreed to.

Mr Trump claims he has received “positive messages” about the ceasefire from Moscow and reiterated on Wednesday that he would “do things financially that would be very bad for Russia” if they did not accept it.

He said that a ceasefire would make sense for Moscow but said there was “a lot of downside for Russia too”, without elaborating.

“We have a very complex situation solved on one side, pretty much solved. We've also discussed land and other things that go with it,” he said.

“We know the areas of land we're talking about, whether it's pull back or not pull back.”

He acknowledged that positive signals from the Russians meant “nothing” until a deal had been signed. Much of Europe and Ukraine believe Mr Putin’s positive signals will continue to mean nothing even after a peace agreement is signed; history is filled with examples of Russia, under Mr Putin’s leadership, breaking ceasefire agreements, they say.

US secretary of state Marco Rubio, who led the delegation in Saudi Arabia, said after the talks that the US would take the offer to Russia, and the ball is in Moscow's court. "Our hope is that the Russians will answer 'yes' as quickly as possible, so we can get to the second phase of this, which is real negotiations," he told reporters.