British Prime Minister Keir Starmer said he would not yield to Donald Trump on his opposition to US demands to acquire Greenland, adding that the US president had reversed his prior support for a Chagos Islands deal to put pressure on Britain.

Starmer has called for “calm discussion” on Greenland and indicated on Monday he did not wish to escalate a trade war, after Trump threatened tariffs on Britain and other European countries unless he was allowed to buy Greenland.

The next day, Trump said Britain had been stupid and weak to agree a deal to cede sovereignty of the Chagos Islands in the Indian Ocean to secure the future of a US-UK air base there. When the deal was announced, Trump’s administration expressed support for it.

Starmer has sought close ties with Trump to preserve trade and security ties, but in some of his sharpest criticisms of Trump, Starmer said he would not be bullied into changing his view that the future of Greenland should be decided by its people and by Denmark.

“I will not yield, Britain will not yield, on our principles and values about the future of Greenland under threats of tariffs, and that is my clear position,” Starmer told lawmakers, adding the Danish prime minister would visit London on Thursday.

Starmer said that Trump’s criticism of the Chagos Islands deal with Mauritius was because “he wants me to yield on my position, and I’m not going to do so”.

“President Trump deployed words on Chagos yesterday that were different from his previous words of welcome and support,” Starmer said.

“He deployed those words yesterday for the express purpose of putting pressure on me and Britain in relation to my values and principles on the future of Greenland.”

In response to questions from lawmakers urging Starmer to go further in standing against Trump, Starmer said it was still important to work with the US on issues such as Ukraine.

“That does not mean we agree with the US on everything,” he said. “But it is foolhardy to think that we should rip up our relationship with the US, abandon Ukraine, and so many other things that are important to our defence, security and intelligence.”