(The Center Square) – President-elect Donald Trump said Tuesday that U.S. economic security depends on controlling Greenland and the Panama Canal.

Trump's comments came the same day his son, Don Jr., landed on the arctic island.

"Don Jr. and my Reps landing in Greenland," the president-elect wrote on Truth Social. "The reception has been great. They, and the Free World, need safety, security, strength, and PEACE! This is a deal that must happen. MAGA. MAKE GREENLAND GREAT AGAIN!"

As Trump prepares to return to the White House for a second term, he has once again brought up the idea of buying or otherwise taking control of the autonomous territory, which is part of Denmark.

In addition to Greenland, Trump said the U.S. should control the Panama Canal and offered to allow Canada to join the nation.

"Many people in Canada LOVE being the 51st State," Trump wrote. "The United States can no longer suffer the massive Trade Deficits and Subsidies that Canada needs to stay afloat. Justin Trudeau knew this, and resigned. If Canada merged with the U.S., there would be no Tariffs, taxes would go way down, and they would be TOTALLY SECURE from the threat of the Russian and Chinese Ships that are constantly surrounding them. Together, what a great Nation it would be!!!"

Trump told reporters during a news conference Tuesday that he wouldn't rule out military intervention or economic penalties to get what he wants.

"I can't assure you, you're talking about Panama and Greenland," Trump told reporters during a new conference at his Mar-a-Lago resort in Florida. "No, I can't assure you on either of those two. But I can say this – we need them for economic security."

Greenland, where about 57,000 people live, is a fully autonomous territory of the Kingdom of Denmark. Greenland's economy is dependent on Danish subsidies and fishing.

In 1867, when President Andrew Johnson bought Alaska, he also considered buying Greenland. The U.S. also tried to buy Greenland in 1946. The United States proposed to pay Denmark $100 million in gold to buy Greenland, according to documents in the National Archives. The sale never went through, but the U.S. got the military base it wanted on the island.

Pituffik Space Base, previously known as Thule Air Base, is located in Greenland. Pituffik SB is locked in by ice nine months out of the year, but the airfield is open and operated year round. Pituffik exists due to agreements between the U.S. and the Kingdom of Denmark, specifically addressing mutual defense, according to Space Force.

None of the countries that Trump has designs on appear eager to sell land to the U.S.

Danish Prime Minister Mette Frederiksen rejected Trump's first proposal to buy Greenland in 2019. Frederiksen called it "absurd" at the time.

On Tuesday, Frederiksen said "Greenland belongs to the Greenlanders."

"There is a lot of support among the people of Greenland that Greenland is not for sale and will not be in the future either," she said, according to a report from Politico.

Panamanian President José Raúl Mulino previously said that Panama's ownership of the canal was "non-negotiable."