"This was the most solid relationship of all. And now we have very strong relationships with other countries in Europe," he said, singling out France and Germany, after UK Prime Minister Keir Starmer's initial refusal to allow the United States to use British military bases in its war with Iran.

Trump said Starmer "has not been helpful", adding: "I never thought I'd see that. I never thought I'd see that from the UK. We love the UK."

In a telephone interview from the White House on Monday evening, Trump said: "This was the most solid relationship of all. And now we have very strong relationships with other countries in Europe."

"It's a different world, actually. It's just a much different kind of relationship that we've had with your country before.

"It's very sad to see that the relationship is obviously not what it was," he added.

The scathing comments come a day after Trump described Starmer's reaction as "very disappointing" in an interview with The Daily Telegraph.

He added that Starmer's later decision to allow the use of UK bases on specific grounds as "useful" but said it "took far too much time".

Any potential military action in the Middle East is politically sensitive in the UK following former prime minister Tony Blair's disastrous support for the US-led invasion of Iraq.

- 'National interest' -

Starmer defended his position to parliament on Monday.

"President Trump has expressed his disagreement with our decision not to get involved in the initial strikes, but it is my duty to judge what is in Britain's national interest," he told lawmakers.

"That is what I have done and I stand by it," he added.

After initially refusing to have any role in the strikes, Starmer on Sunday announced that he had agreed to a US request to use British military bases for a "specific and limited defensive purpose".

His Downing Street office said Starmer took the decision after Iran fired missiles over the weekend that put British interests and people "at risk".

"We all remember the mistakes of Iraq, and we have learnt those lessons. Any UK actions must always have a lawful basis and a viable thought-through plan," he added in parliament.

The prime minister also said that British military bases in Cyprus "are not being used by US bombers" during the US-Israeli war with Iran.

Britain's Akrotiri air force base on Cyprus came under attack by an unmanned Iranian drone that hit the base's runway early on Monday.

Starmer said the strike "was not in response to any decision that we have taken," adding that the British government believed the drone "was launched prior to our announcement".

Iran's approach is becoming "more reckless and more dangerous", Starmer said.

"They are working ruthlessly and deliberately through a plan to strike, not only military targets, but also economic targets in the region, with no regard for civilian casualties. That is the situation we face today and to which we must respond," he added.