Denmark's foreign minister says he will summon the US ambassador to address a report that Washington's spy agencies have been told to focus on Greenland amid Donald Trump's threats to take over the island.

"It worries me greatly because we do not spy on friends," Lars Løkke Rasmussen said, responding to the report in The Wall Street Journal.

According to the newspaper, US spy agencies were told to focus efforts on the semi-autonomous country's independence movement, and American goals to extract mineral resources there.

Director of National Intelligence Tulsi Gabbard accused the Journal of attempts to "undermine" President Trump "by politicizing and leaking classified information".

While not denying the report, she accused the newspaper of "breaking the law and undermining our nation's security and democracy".

Rasmussen, who was attending an EU ministers meeting in Warsaw, said the report was "somewhat disturbing".

"We are going to call in the US acting ambassador for a discussion at the foreign ministry to see if we can confirm this information," Rasmussen said.

"It doesn't seem to be strongly rejected by those who speak out. That worries me."

The Danish Security and Intelligence Service (PET) declined to comment on the article, but told Danish media that it had "naturally" taken note of US interest in Greenland.

Based on international interest in Greenland in general, the agency said, there was an increased espionage threat against it and Denmark.

President Trump has repeatedly vowed to take control of Greenland, most recently telling NBC News on Sunday that he had not ruled out using military force to seize the arctic island.

"I don't say I'm going to do it, but I don't rule out anything," he said. "We need Greenland very badly. Greenland is a very small amount of people, which we'll take care of, and we'll cherish them, and all of that. But we need that for international security."

During a speech to Congress in March, Trump told US lawmakers that "one way or the other, we're going to get it."

Danish officials also condemned a visit to Greenland by Vice-President JD Vance in March.

Danish PM Mette Frederiksen said the visit to a remote US military base "completely unacceptable pressure on Greenland, Greenlandic politicians and the Greenlandic population".

Former President Joe Biden, speaking to BBC News in his first interview since leaving office in January, condemned Trump's calls for the US to take back the Panama Canal, to acquire Greenland and to make Canada the 51st state.

"What the hell's going on here? What president ever talks like that? That's not who we are," Biden told the BBC's Nick Robinson.

"We're about freedom, democracy, opportunity, not about confiscation."

Greenland, the world's largest island, has been controlled by Denmark for about 300 years. The island governs its own domestic affairs, but foreign and defence policy decisions are made in Copenhagen.

The US has long had a security interest in the island. It has had a military base there since World War Two, and Trump may also have an interest in the rare earth minerals that could be mined.

Polls show that the vast majority of Greenlanders want to become independent from Denmark but do not wish to become part of the US.