Last week, Russia’s foreign ministry revealed a draft security agreement with the US and Nato, laying out Moscow’s red lines when it comes to European security.

Some of the proposals of the eight-point document – including asking Nato to bar former Soviet states such as Ukraine from joining the alliance – have been described as untenable and fundamentally contradicting Nato’s own principles.

Senior Russian officials said on Monday that they have not heard from Washington on their proposals yet.

Mr Ryabkov said: “I think they’ll try to turn this into a slow-moving process, but we need it to be urgent, because the situation is very difficult, it is acute, it tends to become more complicated.”

Konstantin Gavrilov, a Russian diplomat in Vienna, said Moscow and Nato had reached a “moment of truth”.

He said: “The conversation needs to be serious and everyone in Nato understands perfectly well, despite their strength and power, that concrete political action needs to be taken, otherwise the alternative is a military-technical and military response from Russia.”

Biden’s response ‘more robust’ than Obama

In 2014 Mr Biden was reportedly overruled by Mr Obama when he took a strong line on sanctions and arming Ukraine following the Crimea annexation. 

Officials said his current response was more proactive and robust than Mr Obama’s, and the White House now has a greater understanding of how much Mr Putin is willing to risk to achieve his objectives. 

However, Ukraine said the military assistance provided by the US so far was appreciated but not enough. 

An adviser to Volodymyr Zelensky, the Ukrainian President, told CNN: “Urgent air and missile defence technology is needed to confront an all-out Russian attack, and this has been requested over a month ago.”

“There is confusion in Kyiv as to why this is being withheld in light of such overwhelming intelligence the Biden administration has shared.”