Trump rattled European leaders by seizing Venezuelan President Nicolas Maduro, who is now detained in New York.
Trump has said the US will “run” Venezuela indefinitely and tap its huge oil reserves.
The US leader has similarly ramped up pressure on Greenland over recent months, saying in December that Russian and Chinese ships were “all over” the territory’s coast.
The foreign ministry in Beijing hit back on Monday, urging Washington to “stop using the so-called China threat as an excuse to seek personal gain”.
Aaja Chemnitz, who represents Greenland in the Danish parliament, accused Trump of “spreading lies about Chinese and Russian warships”.
“The people of Greenland should go into preparation mode,” she told AFP, adding that Greenlanders needed to start taking Trump much more seriously.
On the streets of Copenhagen, people expressed bewilderment at Trump’s threats.
“I think it’s a little crazy that he can say those things,” said Frederik Olsen, 56.
“He has all the access he wants for the troops,” said Christian Harpsoe, 46. “I see no need. You cannot compare this to Venezuela.”