Mr Biden was also advised by senior military officials that the planes would “not appreciably increase” the effectiveness of the Ukrainian air force, and the gain would be “low”.

A senior defence official said: “They [the Ukrainian air force] are not flying their fixed-wing aircraft very much on a daily basis. That’s not, we’re not making a judgment here. It’s just a fact.”

But Mitt Romney, the Republican senator, said: “I believe there’s a sentiment that we’re fearful about what Putin might do and what he might consider as an escalation. It’s time for him to be fearful of what we might do.

“The truth of the matter is his military is exposed in Ukraine, bogged down, unfed, without fuel, they are in a very precarious position.

“He has to think about what happens if he provokes us because they could be obliterated by the forces of Nato. Enough talk. People are dying. Send them [Ukraine] the planes they need.”

‘Ridiculous decision’

Tom Cotton, a Republican who sits on the Senate intelligence committee, accused Mr Biden of “timid hesitating half-measures”.

He said: “There is no intelligence that these aircraft, somehow uniquely, are going to be escalatory in Vladimir Putin’s eyes.

“This is only the policy decision of the president and it is a ridiculous decision, and it makes the United States look ridiculous.”

Mr Cotton added: “It is yet another instance in which Joe Biden has allowed Vladimir Putin to back him down by saying ‘boo’.

“If we continue to blink every time Vladimir Putin says ‘boo’ it’s not going to stop in Ukraine, it’s not going to stop in Europe.”

Mark Milley, America’s top general and the chairman of the Joint Chiefs of Staff, was making phone calls to Republican senators to explain the military advice given to the President, and his decision.