The relationship between Donald Trump and Volodymyr Zelensky was bad enough before the shouting match in the Oval Office.

President Trump had already called him a dictator and said Ukraine started the war – which is a lie.

Now the US-Ukraine alliance nurtured by Joe Biden is in pieces.

The public breakdown also signals a major crisis looming between European members of Nato and the US.

There will be many more doubts and questions about the US commitment to European security outside Ukraine. The biggest is whether President Trump would keep the promise his predecessor Harry Truman made in 1949 to treat an attack on a Nato ally as an attack on America.

Those concerns are based on what appears to be Trump’s determination to restore a strong relationship with Russian President Vladimir Putin.

He has put heavy pressure on Ukraine while offering Putin big concessions – that would have to be made by the Ukrainians.

The security of Ukraine is coming a poor second – and Europeans are worrying theirs is too.

President Zelensky’s refusal to make those concessions has infuriated Trump.

It’s not just the minerals deal that he refused to sign. Ukrainians believe they are in a war for national survival – and that Putin would break any promise to end the war if he is not deterred.

That’s why Zelensky asked repeatedly for American security guarantees.

The meeting ignited into a shouting match after an intervention by Vice-President JD Vance.

There are suspicions now that the public row was – in the words of one diplomatic observer – a planned political mugging: either to force Zelensky to do America’s bidding, or to precipitate a crisis that would allow them to blame him for whatever happens next.

If Trump follows the breakdown of talks with a freeze on military aid, Ukraine will fight on. The questions are how effectively, and for how long.

Pressure will redouble on its European allies to take up the slack.