Sir Keir Starmer urged Donald Trump not to trigger a trade war with Europe over his bid to grab Greenland.
At a press conference in Downing Street, the Prime Minister stressed the US president was “completely wrong” with his tariff threat against eight European nations, including the UK, if they do not allow America to buy Greenland.
“A trade war is in no-one’s interests,” he said.
“My first task is we don’t get to that place,” he added, stressing it would hit British workers, jobs and the UK economy.
He also said he did not believe that Trump was genuinely considering sending US troops to seize Greenland.
But Sir Keir was taking a less confrontational approach to Trump’s Greenland threat compared to some other European leaders including French president Emmanuel Macron who was pushing for preparations for retaliatory action.
The German and French finance ministers said on Monday European powers would not be “blackmailed” and there would be a clear and united response to threats of escalated US tariffs over Greenland.
"Germany and France agree: we will not allow ourselves to be blackmailed," German Finance Minister Lars Klingbeil said at his ministry in Berlin where he received his French counterpart.
"Blackmail between allies of 250 years, blackmail between friends, is obviously unacceptable," French Finance Minister Roland Lescure added at the same event.
Sir Keir sought to defend his way of trying to deal with Trump, saying that an “angry social media post” or “grandstanding” was not a “substitute for hard work”.
But a former Nato chief warned against seeking to “appease” Trump.
Sir Richard Shirreff, ex-Nato Deputy Supreme Allied Commander Europe, said the UK, Canada and other Nato partners should send troops to Greenland ready to fight US forces if necessary to defend the vast, frozen, autonomous Danish territory.
It comes after the US president said he would charge the UK a 10% tariff “on any and all goods” sent to the US from February 1, increasing to 25% from June 1, until a deal is reached for Washington to purchase Greenland from Denmark.
Trump said the same would apply to Denmark, Norway, Sweden, France, Germany, the Netherlands and Finland.
The US president took the drastic step after the eight nations sent a small military team to Greenland, which appears to have angered Trump.
He accused them of “playing this very dangerous game” and threatened tariffs unless they agreed to the “Complete and Total purchase of Greenland” by America.
The UK sent a single military officer for the Arctic endurance exercise, and said in a joint statement with the seven other affected countries that it was planned and posed “no threat to anyone”.
The Prime Minister said the dispute over Greenland, which the US president wants to take over because of its strategic Arctic location and mineral wealth, should be resolved through "calm discussion between allies" rather than military action or a trade war.
He denied that he was being too soft in his dealings with Trump, arguing that his approach has delivered economic benefits to Britain, which struck the first deal with America on tariffs and got a lower rate than the European Union.
"The US remains a close ally on defence, on security and on intelligence, on nuclear capability, we've worked very closely with the United States, and we must never lose sight of our national interest in that," he said.
"But we must stand up for our values.
We must be clear about the principles that we are applying here, and we'll continue to do so on the question of tariffs."
With all the main political parties at Westminster condemning Trump’s actions, Sir Keir added: "This is a moment for the whole country to pull together."
Sir Richard stressed Nato countries should call Trump’s “bluff” but prepare for the “worst” potential outcome in the clash over Greenland.
“Europe and Canada should put troops into Greenland, assuming the Danes agree and they must take the lead...to counter any aggression, whether it’s Russian, Chinese or indeed American,” Sir Richard told Times Radio.
“We have to recognise that with Trump and indeed with Putin, we have to assume the worst case is going to happen and prepare for it.
“Nato...should be war gaming the worst potential case scenarios.
“Appeasement simply does not work.”
He stressed that the future of Nato was under threat.
He added that Trump had thrust a Western military alliance “based on values of liberty, freedom, democracy, rulle of law, and collective defence, and above all trust completely in jeopardy”.
He emphasised that the main impact could be on the Ukraine war, explaining: “If Nato collapses into smithereens because it’s been divided and ruled by the bully, then Putin has open house.”
At an emergency meeting, European Union ambassadors agreed on Sunday to step up their efforts to dissuade Trump from imposing tariffs, while also preparing retaliatory measures should the duties go ahead.
Sir Keir held a series of calls on Sunday afternoon, speaking with Trump as well as Danish prime minister Mette Frederiksen, European Commission president Ursula von der Leyen and Nato chief Mark Rutte.
In all of them, he reiterated his position on Greenland - that its future is for Denmark and Greenland to decide - and that security in the High North is a priority for all Nato allies to protect Euro-Atlantic interests.
“He also said that applying tariffs on allies for pursuing the collective security of Nato allies is wrong,” a Downing Street spokesperson said.
Early on Monday, Trump said Denmark had failed to heed warnings to protect Greenland from the threat of Russia.
He wrote on his Truth Social social media site: “NATO has been telling Denmark, for 20 years, that ‘you have to get the Russian threat away from Greenland’.
“Unfortunately, Denmark has been unable to do anything about it. Now it is time, and it will be done!!!”
It comes as UN secretary-general Antonio Guterres warned the UN has “no leverage” in resolving major global conflicts compared to the “big powers”, adding the US appears to believe its own power is more important than international law.
