WASHINGTON (NEXSTAR) -- President-elect Donald Trump is once again expressing a desire to take over Greenland and the Panama Canal and says he won't rule out using military force to do it.  In a press conference on Tuesday, the incoming president told reporters he would like to seize control of both Greenland and the Panama Canal, arguing that the territories would have benefits for U.S. trade and military power.  "Giving the Panama Canal to Panama was a very big mistake," Trump said. "We need Greenland for national security purposes." When asked if he would rule out the possibility of using military force to take the territories, he refused.  "I'm not going to commit to that. Now it might, it might be that you'll have to do something," Trump said.  His remarks come as his son, Don Trump Jr., is in Greenland for a visit. Greenland's officials say he is there as a private citizen, and he didn't share any thoughts on his father's plan to take the Arctic territory.  "Well, that's not for me to talk about. That's for others to talk about but, we're just excited to be here," Trump Jr. said.  Greenland is a territory of Denmark. On Tuesday, Danish Prime Minister Mette Frederiksen pushed back on the idea of a U.S. takeover. "Greenland is not for sale," Frederiksen said.   The President of Panama, José Raúl Mulino, has also previously rejected Trump's plan.  "The sovereignty and independence of our country are non-negotiable," Mulino said.  President-elect Trump has repeatedly expressed a desire to expand U.S. territory and is promising his upcoming term will be a 'Golden Age of America.’ He also said during the press conference that he wants to rename the Gulf of Mexico and instead call it, 'The Gulf of America.' "The Gulf of America. What a beautiful name," Trump said.