COPENHAGEN, Denmark — Escalating an international spat, President Trump said Wednesday he scrapped his trip to Denmark because the prime minister made a “nasty” statement when she rejected his idea to buy Greenland as an absurdity.

“You don’t talk to the United States that way, at least under me,” Trump told reporters in Washington. “I thought it was not a nice statement, the way she blew me off.”

Danish Prime Minister Mette Frederiksen called the whole thing “an absurd discussion” and said she was “disappointed and surprised” that Trump had canceled his visit.

Trump said Frederiksen’s comment labeling his idea as absurd “was nasty. I thought it was an inappropriate statement. All she had to say was say, ‘No, we wouldn’t be interested.'”

Greenland is a semi-autonomous territory of the U.S. ally, and Frederiksen said the U.S. remains one of Denmark’s close allies.

The political brouhaha over the world’s largest island comes from its strategic location in the Arctic. Global warming is making Greenland more accessible to potential oil and mineral resources. Russia, China, the U.S., Canada and other countries are racing to stake as strong a claim as they can to Arctic lands, hoping they will yield future riches.

Trump was scheduled to visit Denmark on Sept. 2-3 as part of a European tour. But early Wednesday, he tweeted his decision to indefinitely postpone the trip. The move stunned Danes and blindsided the Danish royal palace. Spokeswoman Lene Balleby told The Associated Press that it came as “a surprise” to the royal household, which had formally invited Trump.

The U.S. State Department said Secretary of State Mike Pompeo spoke Wednesday with his Danish counterpart and “expressed appreciation for Denmark’s cooperation as one of the United States’ allies and Denmark’s contributions to address shared global security priorities.”

Spokesperson Morgan Ortagus said Pompeo and Danish Minister of Foreign Affairs Jeppe Kofod “also discussed strengthening cooperation with the Kingdom of Denmark – including Greenland – in the Arctic.”

Denmark’s Prime Minister Mette Frederiksen talks about President Trump’s cancellation of his scheduled state visit after she said it was an absurd idea that the United States would believe it could buy Greenland. She is standing in front of the State Department in Copenhagen on Wednesday. Mads Claus Rasmussen/Ritzau Scanpix

On Tuesday, Trump tweeted, “Denmark is a very special country with incredible people, but based on Prime Minister Mette Frederiksen’s comments, that she would have no interest in discussing the purchase of Greenland, I will be postponing our meeting scheduled in two weeks for another time.”

The vast island of Greenland sits between the Atlantic and Arctic oceans, has a population of 56,000 and has 80% of its land mass covered by a 660,000 square-mile ice sheet.

For all of Greenland’s appeal, scientists consider it the canary in the coal mine for climate change and say its massive ice sheet has seen one of its biggest melts on record this summer, contributing to a global rise in sea levels.

Frederiksen said she is standing behind the government of Greenland.

“A discussion about a potential sale of Greenland has been put forward. It has been rejected by Greenland Premier Kim Kielsen and I fully stand behind that rejection,” she told reporters in Copenhagen.

Frederiksen, who took office two months ago in a minority Social Democratic government, went on to say that diplomatic relations between Copenhagen and Washington “are not in any crisis in my opinion” despite Trump’s canceled plans.

“The invitation for a stronger strategic cooperation with the Americans in the Arctic is still open,” Frederiksen said, adding “the United States is one of our closest allies.”

Others in Denmark were not as gracious.

Martin Lidegaard, a former Danish foreign minister, told broadcaster TV2 that it was “a diplomatic farce” and Trump’s behavior was “grotesque.”

President Trump speaks with reporters before departing on Marine One on the South Lawn of the White House on Wednesday, as he headed to Kentucky. Alex Brandon/Associated Press

Trump’s cancellation was “deeply insulting to the people of Greenland and Denmark,” former Prime Minister Helle Thorning-Schmidt wrote on Twitter.

Claus Oxfeldt, chairman of Denmark’s main police union, told Danish media that authorities had been busy planning the third visit by a sitting U.S. president to the Scandinavian NATO member. “It has created great frustrations to have spent so much time preparing for a visit that is canceled,” Oxfeldt was quoted as saying.

Ordinary Danes shook their heads at the news, with many calling Trump immature.

“He thinks he can just buy Greenland. He acts like an elephant in a china shop,” said Pernille Iversen, a 41-year-old shopkeeper in Copenhagen.

“This is an insult to (Queen) Margrethe, to Denmark,” said Steen Gade, a 55-year-old road worker.

In Greenland, Johannes Kyed, an employee with a mine company, told Denmark’s TV2 channel that wanting to buy a country and its people is a relic of the past.

“This is not the way the world works today,” Kyed said.

The U.S. ambassador to Denmark, Carla Sands, was apparently not informed of Trump’s decision ahead of time.

Shortly before Trump canceled the trip on Twitter, she sent a tweet saying “Denmark is ready for POTUS,” using an acronym for “President of the United States” along with Trump’s Twitter handle and a photo from Copenhagen’s City Hall square, where a Dane had paid for two pro-Trump ads on giant electronic screens.

Trump said Sunday he was interested in buying Greenland for strategic purposes, but said a purchase was not a priority for his government at this time. Both Frederiksen and Greenland leader Kielsen responded that Greenland is not for sale.

“The Prime Minister was able to save a great deal of expense and effort for both the United States and Denmark by being so direct,” Trump said in the tweet Wednesday. “I thank her for that and look forward to rescheduling sometime in the future!”

Trump is still expected to visit nearby Poland beginning Aug. 31.

Retreating ice could uncover potential oil and mineral resources in Greenland which, if successfully tapped, could dramatically change the island’s fortunes. However, no oil has yet been found in Greenlandic waters and the thickness of the ice means exploration is only possible in coastal regions.

Even then, conditions are far from ideal, due to Greenland’s long winters with frozen ports, 24-hour darkness and temperatures that regularly drop below minus 22 Fahrenheit in the island’s northern regions.

American leaders have tried to buy Greenland before. In 1946, the U.S. proposed paying Denmark $100 million to buy Greenland after flirting with the idea of swapping land in Alaska for strategic parts of the Arctic island.

Under a 1951 deal, Denmark allowed the U.S. to build bases and radar stations on Greenland.

The U.S. Air Force currently maintains one base in northern Greenland, Thule Air Force Base, 745 miles south of the North Pole. Former military airfields in Narsarsuaq, Kulusuk and Kangerlussuaq have become civilian airports.

The Thule base, constructed in 1952, was originally designed as a refueling base for long-range bombing missions. Since 1961, it has been a ballistic missile early warning and space surveillance site.

Associated Press writer Darlene Superville in Washington contributed to this report.