A Republican congressman from Florida introduced a bill Monday to annex Greenland and make it the 51st U.S. state as President Trump threatens to seize the autonomous Danish territory.

Mr. Trump has said the United States will take Greenland "one way or the other," floating the idea of buying the territory or taking it by force, despite strong pushback from Denmark, a NATO ally.

Rep. Randy Fine said his new legislation would authorize Mr. Trump "to take whatever steps necessary to annex or acquire Greenland."

It would also require the Trump administration to send a report to Congress detailing changes to federal law that would allow the Arctic island to become a U.S. state.

"Greenland is not a distant outpost we can afford to ignore -- it is a vital national security asset," Fine said in a statement.

Meantime, Democratic Rep. Jimmy Gomez of California was planning to introduce legislation that would block federal funds from being used to pay for any of Mr. Trump's plans to take over Greenland, the Reuters news agency reports.

Mr. Trump has insisted that Greenland, rich in rare earth mineral resources, needs to be brought under U.S. control, arguing the territory is crucial for national security.

He has said Russia or China would take Greenland if the U.S. doesn't.

Democrats and Republicans alike have pushed back on his rhetoric, and Danish Prime Minister Mette Frederiksen has warned that an armed attack on Greenland from the U.S. would spell the end of NATO, the 32-member military alliance. 

NATO and Greenland's government on Monday said they intended to work on strengthening the defense of the territory — a key concern cited by Mr. Trump.

Greenland's Prime Minister and Premier Jens-Frederik Nielsen said at a press conference Wednesday that "we choose Denmark over the U.S.," adding "I would like to repeat that Greenland is not for sale."

Danish Prime Minister Mette Frederiksen noted that "there is much evidence that the hardest part now lies ahead of us." 

Trump administration officials are set to meet with Danish officials about Greenland on Wednesday, diplomatic sources confirmed to CBS News earlier this week. Danish media reported Tuesday that Vice President JD Vance, who traveled to Greenland last year, would be among them.