LONDON — Keir Starmer insisted Wednesday the U.K. “will not yield” to Donald Trump’s demand to seize Greenland — even if the U.S. president imposes tariffs on his NATO allies.

The British prime minister, who has gone to great lengths to foster good relations with Trump since he returned to the White House last year, has deployed his strongest rebuttal of the U.S. president’s territorial ambitions yet.

“I will not yield, Britain will not yield on our principles and values about the future of Greenland under threats of tariffs,” the British prime minister said at weekly prime minister’s questions.

Starmer said Trump’s change of position on Britain’s decision to hand control of the Chagos Islands — home of a joint U.K.-U.S. military base at Diego Garcia — to Mauritius, is designed to put pressure on the U.K. over its Greenland stance.

The U.S. president blindsided London with a Truth Social post early Tuesday morning describing the Chagos deal as an act of “great stupidity.” 

“President Trump deployed words on Chagos yesterday that were different to his previous words of welcome and support when I met him in the White House,” 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.”

Starmer reiterated his belief Greenland’s future is “for the people of Greenland and the Kingdom of Denmark alone,” telling U.K. lawmakers the U.S. president’s threat of economic sanctions is “completely wrong.”

Danish Prime Minister Mette Frederiksen will visit the U.K. Thursday for “bilateral talks.” Starmer said.

Liberal Democrat Leader Ed Davey, a staunch critic of the U.S. president, accused Trump of “acting like a crime boss [and] running a protection racket.” He said Starmer should follow Canadian PM Mark Carney, and French President Emmanuel Macron “in standing up far more strongly to President Trump.”