Donald Trump has revived his bid for the US to acquire Greenland, threatening to pull all American armed forces out of Europe after it repeatedly pushed back.

Arriving at the Nato summit in Ankara on Tuesday, the US president also suggested his commitment to defending Europe had been tempered by political decisions by leaders on immigration and energy.

Keir Starmer and European allies have been determined to avoid another public bust-up with Trump over defence spending after a bruising year for Nato, in which the Iran war once again exposed cracks in the alliance.

The UK has already pushed back on criticism from the US that some allies are “lagging behind” on funding, with the US president expected to rebuke countries, including the UK, for not making enough progress on hitting the target of spending 3.5% of GDP by 2035.

As he arrived in Turkey, Trump suggested that Starmer’s decision to keep out of the war against Iran had contributed to his downfall as prime minister, whereas his stance had in fact been popular with the British public.

“I was very disappointed with Nato. We weren’t treated well because we did something in Iran. We don’t need anybody’s help, but before I asked they said they wouldn’t be there,” the US president told reporters.

“In the case of the United Kingdom, the prime minister, I guess he’s no longer there, maybe because of this, it was a very unpopular thing he did. He said ‘no we’ll help after the war is over’. I said, ‘we don’t need that kind of help’.”

Reviving an earlier row, Trump also suggested that the disagreement about the ownership of Greenland – which is part of Denmark, a fellow Nato member – had “hurt” his relationship with the military alliance.

“Denmark doesn’t spend money to really help Greenland, but it’s an important part for the US, and it’s surrounded by China ships and Russian ships … [It] should be controlled by the US, not by Denmark. And when they wouldn’t go along with it, and with all the money we spend to help them with Russia,” he said.

“We don’t have to spend any money; we could remove all of our soldiers out of Europe because, as you probably noticed, Europe’s a very different place than it was 20 years ago … They better be careful with immigration and energy. If they’re not careful with those two things, you’re not going to have a Europe any more.”

In response, Rachel Reeves, the UK chancellor, told reporters: “The future of Greenland is up to the people of Greenland and of Denmark, and not up to the US president. I’ve been very clear about that ever since it was first suggested.”

Trump also renewed his criticism that Nato allies do not spend enough on defence and are too reliant on the US – an argument European members are attempting to take head-on by announcing multi-billion-pound defence collaborations.

“Why are we spending hundreds of billions of dollars and they’re not there for us? We’ve always been there for them,” he said, although Nato’s mutual defence clause has only ever been triggered after the September 11 attacks on New York, where allies joined US troops in Afghanistan.