Rep. Mike Waltz, R-Fla., President-elect Donald Trump's incoming national security adviser, is supportive of Trump's idea of annexing Greenland.

"This is not just about Greenland," Waltz said in a televised interview. "This is about the Arctic. You have Russia that is trying to become king ... this is about critical minerals; this is about natural resources … it's oil and gas. It's our national security. It's critical minerals."

Trump said at a press conference Tuesday he would not rule out using economic or military pressure on Greenland, insisting the United States needs it "for economic security."

"The U.S. needs Greenland for national security purposes," Trump said, adding that "people really don't even know if Denmark has any legal right to it, but if they do, they should give it up because we need it for national security. That's for the free world. I'm talking about protecting the free world."

He added there are Chinese and Russian ships "all over the place" near Greenland, which the U.S. would not permit.

"The people are going to probably vote for independence or to come into the United States," Trump said, adding if Denmark would not give up control, then he would impose tariffs on Copenhagen at a "very high level."

Donald Trump Jr., who just returned from Greenland, told Newsmax on Tuesday there is a groundswell of support among the people he met that would love to see the Arctic territory have an "alliance" with the United States instead of Denmark.

"They made it very clear that Denmark has prevented them from utilizing some of the incredible natural resources that Greenland has to offer," Don Jr. said. "They basically are treated like second-class citizens. When they go to Denmark, when they go to Copenhagen, numerous young guys told us, 'Hey, we're told to "go home, Inuit, go home Eskimo."'

"They don't love the way that they've been treated."

• Trump Open to Max Pressure on Greenland, Panama Canal
• Donald Trump Jr. to Newsmax: Greenlanders Want 'Alliance' With US