Downing Street said the prime minister “set out his position on Greenland” in a phone conversation with Donald Trump after the US president’s continued threats to take over the territory.
While specific details of Sir Keir Starmer’s comments were not provided, the discussion follows suggestions from US officials that America could potentially use “military means” to acquire the semi-autonomous Danish territory.
Trump has previously claimed the island is crucial for US national security.
It is the first time the pair have spoken since the president launched a raid on Caracas and captured the Venezuelan president.
Cabinet minister Pat McFadden said Wednesday’s call was “just the latest episode in a really important dialogue and relationship”, telling BBC Breakfast: “The economic, security cooperation between US and the UK is really important, and on a security front this is something that keeps British people safe every day.”
While the UK government has refused to condemn US action in Venezuela, Sir Keir has repeatedly stated that Greenland’s future must be determined solely by its own people and Denmark, a stance he reiterated in the Commons earlier the same day.
The ongoing controversy surrounding Greenland has cast a shadow over relations between the US and Europe, with Denmark’s prime minister warning that a US takeover would spell the end of the Nato alliance.
The US secretary of state, Marco Rubio, had earlier said Mr Trump was examining how to “acquire Greenland”, suggesting the US could offer to buy the territory but adding it “retains the option” to use force.
But writing in The Spectator, Lord Peter Mandelson, who was sacked as ambassador to the US last year over his connections with the paedophile financier Jeffrey Epstein, accused European nations of engaging in “histrionics about Greenland” due to their “growing geopolitical impotence”.
Arguing that Mr Trump was not going to “invade” Greenland, he dismissed concerns about sovereignty and Nato’s future as “performative” and called for a “considerably beefed-up role” for America in the territory to counteract threats from Russia and China.
Sir Keir’s call with Mr Trump comes as deputy prime minister David Lammy prepares to meet US vice-president JD Vance on Thursday.
The meeting, at which Greenland is likely to feature, forms part of Mr Lammy’s visit to the US to mark the 250th anniversary of America’s declaration of independence from Britain.
The two men are long-standing friends, with Mr Lammy hosting Mr Vance and his family last year at Chevening, his grace-and-favour house in Kent.
Wednesday’s call also saw Sir Keir and Mr Trump discuss the seizure of oil tanker Marinera earlier in the day, continuing negotiations on the future of Ukraine and US military action in Venezuela.
US forces seized the Russian-flagged oil tanker in the Atlantic on Wednesday in a dramatic move that could put Mr Trump on a collision course with Vladimir Putin.
The UK later revealed British armed forces provided support to the US capture of the vessel as it travelled north and eastwards through the waters between Iceland and Scotland on Wednesday.
The capture of the Marinera could prove to be a new flashpoint in relations between the West and Moscow after Russia’s transport ministry appeared to suggest that international maritime law had been breached.
It comes amid continued negotiations to secure peace in Ukraine, with the UK and France committing to deploying troops in the event of a peace deal.
Meanwhile, the US has signalled it will provide a security guarantee to the European-led peacekeeping efforts, something which Mr Trump has previously appeared reluctant to do.
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