The US President abruptly cancelled his planned September 2-3 visit to Denmark on Tuesday, after PM Mette Frederiksen called his idea to buy the Arctic territory "an absurd discussion”.
After he was once again questioned on Ms Frederiksen’s remarks, Trump told reporters: "You don't talk to the United States that way, at least under me."
He added that calling the discussion absurd "was nasty”, and said: "I thought it was an inappropriate statement. All she had to say was say, ‘No, we wouldn't be interested’”.
Ms Frederiksen later that the US remains one of Denmark's close allies.
The dispute over the world's largest island comes from its strategic location in the Arctic.
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Global warming is making Greenland more accessible to potential oil and mineral resources, and Russia, China, the US, Canada and others are racing to stake a claim, hoping they will yield future riches.
Ms Frederiksen has said Denmark does not own Greenland which belongs to its people. It is part of the Danish realm along with the Faeroe Islands, another semi-autonomous territory, and has its own government and parliament, the 31-seat Inatsisartut.
The sparsely populated island, which is four times zones behind Copenhagen, became a Danish colony in 1775 and remained that way until 1953, when Denmark revised its constitution and made the island a province.
I promise not to do this to Greenland! pic.twitter.com/03DdyVU6HA— Donald J. Trump (@realDonaldTrump) August 20, 2019
....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. I thank her for that and look forward to rescheduling sometime in the future!— Donald J. Trump (@realDonaldTrump) August 20, 2019
In 1979, Greenland and its 56,000 residents who are mainly indigenous Inuits, got extensive home rule but Denmark still handles its foreign and defence policies, as well as currency issues.
Denmark, which considers Greenland as an equal partner, pays annual subsidies of 4.5 billion kroner (£550 million) to Greenland whose economy otherwise depends on fisheries and related industries.
On Wednesday, the US State Department said Secretary of State Mike Pompeo spoke 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”.
Spokesman Morgan Ortagus said Mr Pompeo and Danish Minister of Foreign Affairs Jeppe Kofod "also discussed strengthening cooperation with the Kingdom of Denmark - including Greenland - in the Arctic”.
"Appreciate frank, friendly and constructive talk with @SecPompeo this evening, affirming strong US-DK bond," Mr Kofod tweeted on Wednesday evening.
"US & Denmark are close friends and allies with long history of active engagement across globe."