Some were alarmed by the disunity among leading US political figures.

John Brennan, former Director of the CIA, said: “I am currently in the UK, watching Republicans greet Putin’s invasion of Ukraine with criticisms of President Biden.

“I am being constantly asked, ‘What has happened to the Republican Party?’  Sadly, my only answer is, ‘It has lost its very soul’.”

Meanwhile, Democrats praised Mr Biden for uniting Nato allies in their response to Mr Putin.

Steny Hoyer, the Democrat leader in the House, said: “These unified steps make clear that the United States and our allies are not bluffing in our determination to inflict serious and painful consequences on Russia.”

Senator Chris Coons, a close ally of the president, said Mr Biden had been “strong” and that additional “waves” of sanctions would be “crushing” for Russia.

Mr Biden has steered clear of cutting Russia out of SWIFT, the international bank transaction system.

Democrats said it was among the “mother of all sanctions” and a US official said it “remains an option”.

A senior Biden administration official said: “We are ready to press a button to take further action on the very largest Russian financial institutions.”

But Lindsey Graham, the Republican senator, said the actions taken so far were “woefully inadequate” and called for a “sanctions regime from hell”.

He said: “This is a critical moment in history and President Biden is not seizing the moment.”