Prime Minister Sir Keir Starmer has directly challenged US President Donald Trump, declaring it "wrong" to impose tariffs on NATO allies for participating in collective security exercises. The rebuke came during a series of urgent diplomatic calls on Sunday, 18 January 2026.
A Flurry of Diplomatic Calls
The confrontation stems from President Trump's unexpected announcement that he would levy a 10% tariff "on any and all goods" sent to the US from the United Kingdom, effective from 1 February. This tariff is set to rise sharply to 25% from 1 June unless a deal is reached for Washington to purchase Greenland from Denmark.
The same punitive trade measures were threatened against Denmark, Norway, Sweden, France, Germany, the Netherlands, and Finland. In response, Sir Keir held a rapid sequence of telephone discussions on Sunday afternoon, speaking not only with President Trump but also with Danish Prime Minister Mette Frederiksen, European Commission President Ursula von der Leyen, and NATO Secretary General Mark Rutte.
The Greenland Dispute Explained
The trigger for the tariff threat appears to be a Danish-led military exercise, named Arctic Endurance, conducted with allied nations in Greenland this week. President Trump publicly questioned the manoeuvre, stating the involved countries had "journeyed to Greenland, for purposes unknown".
However, the UK and other participating nations were quick to stress the exercise was long-planned and routine. The UK's involvement was minimal, consisting of a single military officer. A joint statement from the affected allies clarified: "As members of NATO, we are committed to strengthening Arctic security as a shared transatlantic interest. The pre-coordinated Danish exercise Arctic Endurance conducted with Allies, responds to this necessity. It poses no threat to anyone."
Transatlantic Unity and Warning
According to a Downing Street spokeswoman, Sir Keir was unequivocal in all his conversations. "In all his calls, the Prime Minister reiterated his position on Greenland," she said. "He said that security in the High North is a priority for all NATO allies in order to protect Euro-Atlantic interests. He also said that applying tariffs on allies for pursuing the collective security of NATO allies is wrong."
The allied nations issued a stern collective warning, arguing that the US tariff threats "undermine transatlantic relations and risk a dangerous downward spiral". They pledged to remain "united and coordinated" in their response. Reports from the US suggest the European allies were given no prior warning of the impending tariff announcement, despite Washington's known interest in Greenland.
