The United States and European powers have warned Russia that any new attack on Ukraine would trigger a swift, painful and united response from the West, as top-level diplomatic efforts intensified to defuse the security crisis in eastern Europe.
US president Joe Biden welcomed new German chancellor Olaf Scholz to the White House on Monday, as French president Emmanuel Macron held talks with Russian counterpart Vladimir Putin in the Kremlin and four European foreign ministers visited Kyiv.
“We’re working in lockstep to further deter Russian aggression in Europe,” Mr Biden said beside Mr Scholz, amid a continuing build-up of some 100,000 Russian troops and heavy weapons near Ukraine.
Mr Biden vowed that in the event of a new attack on Ukraine, the West would ensure that a major new Russian-German gas pipeline never became operational.
“If Russia invades – that means tanks and troops crossing the border of Ukraine again – then there will be no longer a Nord Stream 2,” Mr Biden said.
Mr Scholz did not comment directly on Nord Stream 2, but said Germany and the US were "one voice and do things together, and we made it very clear if there was military aggression against Ukraine, this will entail severe consequences that we agreed upon together".
“We are in a very difficult situation,” he added. “There is a military threat against Ukraine, we cannot remain silent on that. We see a number of troops along the Ukrainian border and that is a serious threat to European security and this is why it is important that we act together, stand together and do what it necessary together.”
Both leaders said they did not know whether Russia would launch a new attack on Ukraine, but Mr Biden said American citizens would “be wise to leave the country ... I’d hate to see them get caught in the crossfire if in fact they did invade”.
After more than five hours of talks in Moscow, Mr Putin said the West had still failed to address Russia's demands for Nato to rule out further expansion in eastern Europe and withdraw its military presence from current members in the region.
He also accused the West of stoking tension by sending weapons and “military instructors and trainers” to Ukraine, and claimed that future Nato membership for the country would immediately place the alliance in direct conflict with Russia over Crimea.
Mr Putin also accused Kyiv's pro-western government of failing to fulfil the so-called Minsk agreements that are aimed at ending the war in eastern Ukraine and of discriminating against the country's Russian speakers.
Mr Macron – who will be in Kyiv on Tuesday – called for de-escalation of tension around Ukraine and insisted that Nato’s “open-door” policy was not negotiable.
Despite their clear disagreements, however, both leaders said diplomacy on disputed security issues would continue.
Russia denies planning a new attack on Ukraine but has massed forces close to its borders while threatening to take “military-technical” measures if its security demands are not met.
EU foreign policy chief Josep Borrell described the crisis as "the most dangerous moment for the security in Europe after the end of the cold war" after talks with US secretary of state Antony Blinken in Washington.
Mr Blinken said the US had “developed a high-impact, quick-action response that would inflict massive costs on the Russian economy and financial system including sanctions and significant export control ... We and our allies and partners are united across the board”.