Donald Trump has declared that United States control over Greenland is “vital” to his proposed Golden Dome air and missile defence system, sharpening tensions with Denmark and injecting new urgency into the strategic contest for the Arctic.

In a social media post, Trump argued that Washington must secure Greenland, an autonomous territory within the Kingdom of Denmark, to guarantee US national security and strengthen NATO’s northern defences.

“The United States needs Greenland for the purpose of National Security. It is vital for the Golden Dome that we are building,” he wrote, insisting that the alliance would be “far more formidable and effective with Greenland in the hands of the UNITED STATES. Anything less than that is unacceptable.”

The remarks mark the latest escalation in Trump’s long-running fixation with Greenland, a vast, sparsely populated island that has become a focal point of great-power rivalry as climate change opens new sea routes and exposes untapped natural resources. The island also occupies a critical position for missile warning, air defence and undersea surveillance between North America and Eurasia.

Trump’s comments landed just as senior Danish and Greenlandic officials were preparing to visit the White House for talks with Vice President JD Vance and Secretary of State Marco Rubio. The meeting, billed as a high-level discussion on Arctic security and the future of US presence on the island, was overshadowed by the president’s renewed insistence that American control is non-negotiable.

In Copenhagen, Danish Defence Minister Troels Lund Poulsen moved quickly to reassure Washington that Denmark takes the security of Greenland seriously. Speaking to reporters, he said Denmark was already increasing its military footprint in the Arctic and was in discussions with allies about “an increased NATO presence in the Arctic.”

Denmark, which has long hosted US military facilities in Greenland, including the key Thule Air Base in the island’s northwest, has traditionally framed its role as both a security guarantor and a protector of Greenlandic autonomy. Poulsen’s comments appeared aimed at balancing those responsibilities while signalling that Copenhagen is willing to deepen cooperation, but not to relinquish sovereignty.

Trump, however, suggested that NATO should go further and take a leading role in constructing the Golden Dome, a multi-layered missile defence architecture he has promoted as a shield against long-range threats from adversaries such as Russia, China, Iran and North Korea.

“NATO should be leading the way,” he wrote, warning that if the alliance failed to act decisively, rivals would seize the initiative. “IF WE DON’T, RUSSIA OR CHINA WILL, AND THAT IS NOT GOING TO HAPPEN!”

Strategists have long viewed Greenland as a linchpin in the defence of North America. During the Cold War, US early-warning radars and airfields on the island formed part of the first line of detection against Soviet bombers and ballistic missiles crossing the Arctic. Today, as Russia modernises its Arctic bases and China brands itself a “near-Arctic state” while investing in polar research and infrastructure, the island’s importance has only grown.

US military planners see Greenland as a natural platform for long-range sensors, anti-missile systems, and air and naval operations that could monitor and, if necessary, intercept threats approaching over the polar region. The Golden Dome concept, as described by Trump and some of his advisers, would integrate space-based sensors, ground-based interceptors, and advanced radar networks into a seamless shield stretching across the northern hemisphere.

Control over Greenland, in Trump’s view, would allow Washington to harden that shield, reduce reliance on allied permissions, and pre-empt any attempt by Russia or China to gain a foothold on the island through economic or scientific partnerships. US officials and analysts have previously expressed concern about Chinese interest in building airports, mining operations and research facilities in Greenland, warning that such projects could have dual-use military potential.

Trump has repeatedly floated the idea of taking over Greenland outright, reviving a notion that dates back to the early Cold War, when the United States quietly explored the possibility of purchasing the island from Denmark. While those efforts never materialised, Washington did secure long-term defence agreements and the right to operate bases there.

In recent years, Trump has spoken more bluntly, at times framing the issue as a straightforward transaction and at other times as a matter of strategic necessity. His latest comments suggest he feels emboldened by what he portrays as decisive action abroad, including a controversial strike in Venezuela that removed its president and, in his telling, demonstrated American resolve.

For Denmark and Greenland, Trump’s rhetoric presents a delicate challenge. Greenland’s government has steadily pushed for greater autonomy and eventual full independence, while relying heavily on Danish financial support and security guarantees. Many Greenlanders welcome increased US investment and security cooperation, but the idea of a transfer of sovereignty to Washington is deeply contentious.

Danish leaders, across the political spectrum, have consistently rejected any suggestion that Greenland is for sale or that its status can be altered without the consent of its people. They have instead emphasised partnership: more joint exercises, more intelligence sharing, and more infrastructure investment, particularly in dual-use facilities that can serve both civilian and military needs.

NATO officials, for their part, have been cautious in public, acknowledging the Arctic’s growing strategic importance while avoiding direct endorsement of any change in Greenland’s sovereignty. The alliance has, however, stepped up its focus on the High North, with more exercises in the Norwegian and Greenland Seas and renewed attention to undersea cables, maritime chokepoints and air defence corridors.

Behind the scenes, diplomats and defence planners are grappling with how to reconcile Trump’s maximalist demands with the legal and political realities of the North Atlantic. Any attempt by Washington to unilaterally assert control over Greenland would trigger a major crisis with Denmark, strain NATO unity and likely provoke counter-moves from Moscow and Beijing.

At the same time, few in the alliance dispute Trump’s underlying premise that whoever shapes the future of Greenland will wield enormous influence over the Arctic. Melting sea ice is opening the fabled Northwest Passage and other routes that could shorten shipping times between Asia, Europe and North America, while also creating new vulnerabilities for coastal states and maritime trade.

Greenland’s mineral wealth, including rare earth elements, further complicates the picture. As the global race for critical minerals intensifies, the island’s deposits have drawn interest from companies and governments seeking to reduce dependence on existing suppliers. For Washington, securing access to those resources while denying them to rivals dovetails with broader economic and security goals.