Joe Biden’s visit to Europe at a time of acute crisis for the Continent should have been a reassuring event. Here was the leader of what is still the world’s only true superpower reaffirming America’s commitment to Nato and to the defence of freedom in the face of aggression.

That it has turned into yet another gaffe-strewn embarrassment is more than unfortunate. Given the circumstances, his faltering performance is becoming dangerous.

President Biden said many of the right things in Brussels, where he attended a Nato summit to discuss the response to Russia’s invasion.

He then travelled to Warsaw to offer support to a country not only taking in the bulk of refugees but also on the front-line of any further incursion from the east. The message has been spelled out to Vladimir Putin in stark terms: one step into Nato territory will be met with a military response.

But Mr Biden, despite many years at the centre of Washington politics, seems remarkably injudicious with his language. His delivery does not inspire confidence but, worse, he says things that are almost instantaneously revoked by his own White House officials. In Warsaw he departed from his script to say of Putin: “For God’s sake, this man cannot remain in power.” Mr Biden may have been voicing the thoughts of millions, but to say it out loud is to invite the question: is America going to topple him then?

Russia is not Iraq and Putin is not Saddam Hussein. A war aimed at regime change is not feasible so why raise the prospect that it might be? Moreover, the very suggestion feeds into the Kremlin’s paranoia that the West is intent on destroying their country, a view inculcated into the Russian psyche for centuries.

Within minutes of Mr Biden’s otherwise stirring speech his team was desperately trying to row back, and not for the first time. He said last week that the US would respond “in kind” if Russia used chemical weapons, which the White House then “clarified” without saying precisely what he meant.

He then implied that American troops based in Poland might be sent to Ukraine, which Washington had to deny, and has been accused of encouraging Putin by stating last month that a “minor incursion” might be acceptable.

At times like this, the free world looks to the US president for leadership and diplomatic proficiency. Both are sorely lacking.