Polish Prime Minister Donald Tusk has warned that the North Atlantic Treaty Organisation could "lose its meaning" if infighting starts erupting within the military bloc, voicing strong support for Denmark amid its recent spat due to US' renewed claims of annexing Greenland.

"No member should attack or threaten another member of the North Atlantic Treaty Organisation. Otherwise, NATO would lose its meaning if conflict or mutual conflicts occurred within the alliance," Tusk told media in Warsaw, as per EU media reports.

Tusk's intervention came as Europe's many NATO member-states, such as France, the UK, Germany, Italy, and Spain, issued a joint declaration affirming unanimous support for Denmark, and its sovereign claims over the semi-autonomous island state.

"Greenland belongs to its people. It is for Denmark and Greenland, and them only, to decide on matters concerning Denmark and Greenland," the statement read.

The Washington-Copenhagen row intensified severely in the past week after renewed remarks by President Donald Trump, and officials from his administration, that the US needs Greenland for strategic reasons and thus should explore various options to secure it, including military ones if needed, alarming the European capitals and Copenhagen.

Danish Prime Minister Mette Frederiksen, in a bitter vocal criticism of Trump's statement, cautioned that any US attack on a NATO ally would effectively turn the whole bloc redundant and bereft of purpose.

"If the US chooses to attack another NATO country militarily, then everything stops," she said, stressing that Greenland is covered by Denmark's NATO membership and collective defence guarantees.

Greenland's own leadership has also rejected calls for a transfer of control, with PM Jens-Frederik Nielsen calling the rhetoric "insulting" and "unacceptable", saying the island is "not an object of superpower rhetoric" and urging a halt to "fantasies of annexation".

European governments have sought to balance firm support for Denmark's sovereignty with appeals to maintain transatlantic ties that underpin NATO and broader security cooperation.

Tusk stated that when push comes to shove over the issue, Copenhagen could "count on the solidarity of the whole of Europe", stressing that transatlantic cooperation should not suffer in the coming days and months.

The recent controversy was notably exacerbated by statements from Trump's White House Deputy Chief of Staff for policy Stephen Miller, who asserted that Greenland "should" belong to Washington and described Washington's position as seeking to integrate the island into its broader security architecture — comments that were condemned by European leaders as dangerous and destabilising.

The strategic Arctic territory has become a flashpoint between Europe and the US, due to its location which is between North America and Europe, as well as having proximity to Russian and Chinese military activity, making it a an object of vital strategic interest.

As tensions persist, European allies continue to emphasise that any discussion about Greenland's future must respect international law, national sovereignty and the core principle that NATO members do not threaten or seize the territory of one another, underscoring the bloc's deep tensions and underlying cracks.