“This is not a serious proposal from a man who wants peace,” he wrote.

“When I met Russian President Vladimir Putin for the first time as Nato secretary general, he opened our meeting by telling me he wanted to disband Nato. If Nato allies engage with Russia’s most recent proposals… they will be directly helping him move a step closer to achieving his goal.”

The White House said that Mr Biden promised Volodymyr Zelenskiy, the president of Ukraine, in a phone call on Sunday that the US would not make any agreements about Ukraine without consulting Kyiv and would act “decisively” in the event of a Russian attack.

Josep Borrell, the European Union’s foreign policy chief, will this week visit the frontline in eastern Ukraine in a show of solidarity, his office announced on Monday.

History of Russia’s cold relationship with Nato

With 30 members, Nato was formed in 1949 as a US-led defensive pact to deter Soviet aggression in Europe during the Cold War.

Following the collapse of the Soviet Union, the bloc accepted as members several former communist countries, including Poland, Hungary and the Baltic states.

Mr Putin and other Russian officials have repeatedly complained about that expansion, saying that it undermined Russia’s security and breached verbal promises given to Mikhail Gorbachev, the former Soviet leader. Western leaders deny making any such promise.

Many in Moscow argue that Mr Putin’s 2014 annexation of Crimea and military intervention in eastern Ukraine were prompted by Western failure to take those complaints seriously.