British Prime Minister Keir Starmer said on Monday that calm discussion between allies was needed on Greenland and that a trade war was not in anyone's interest, after United States President Donald Trump threatened tariffs to secure the territory.

Starmer told an emergency press conference on Monday that the alliance with the US had provided security and prosperity to Britain for decades, and said he would work to maintain those ties and defuse the tensions around Greenland that have thrown the future of NATO into doubt.

However, he said Trump's threats to impose escalating tariffs on Britain and European allies until the US was allowed to buy Greenland was wrong. He said the future of Greenland must be decided by its people and Denmark alone, and that historic alliances must endure.

"Tariffs should not be used against allies in this way,” Starmer said, adding that Britain would be pragmatic and not passive, but he was not looking to escalate a tariff war at this point.

"A tariff war is in nobody's interests, and we have not got to that stage. And my focus, therefore, is making sure we don't get to that stage."

Trump has threatened tariffs on eight countries which sent small numbers of military personnel to Greenland last week, following Trump's repeated statements that he wanted to take over Denmark's vast Arctic island.

Starmer said he had spoken to Trump on Sunday and told him that those forces were "clearly there to assess and work on risk from the Russians". He said he hoped that there was now "real clarity" about that.

Starmer's suggestion that Britain would not retaliate against US tariffs contrasts with the response of the European Union, where officials have discussed options to respond, including a package of tariffs on 93 billion euros ($107.7 billion) of US imports.

The prime minister said the threats risked causing a "downward spiral" for Britain, in terms of trade and the weakening of alliances.

"I do not want to see that happen," he said, adding "that doesn't mean that we put to one side our principles and our values. Quite the contrary, we're very clear about what they are."

Starmer has built a solid relationship with Trump, and in May last year, became the first leader to secure a deal to lower some tariffs.

When asked if he thought Trump was genuinely considering military action, Starmer stated, "I don't, actually. I think that this can be resolved and should be resolved through calm discussion."