President-elect Donald Trump refused on Tuesday to rule out the use of military or economic coercion to force Panama to give up control of the canal that America built more than a century ago and to push Denmark to sell Greenland to the United States.

In a rambling, hourlong news conference, Trump repeatedly returned to the theme of American sacrifice in building the canal and accused China, falsely, of operating it today. When pressed on the question of whether he might order the military to force Panama to give it up — in violation of treaties and other agreements reached during the Carter administration — or to do the same with Greenland, he said: “No, I can’t assure you on either of those two.”

“We need them for economic security — the Panama Canal was built for our military,” he said. Asked again if he would rule out the use of military force, he said: “I’m not going to commit to that. You might have to do something.”

Trump’s statements propelled his repeated calls for expanding U.S. territory to a new level, one that is bound to roil three American allies — Panama; Denmark, which handles Greenland’s foreign and security affairs; and Canada, which he has mocked as America’s “51st state.” On Tuesday he made clear, though, that he was not joking, suggesting that if Canada remained a sovereign state, the financial cost to its trading relationship with the United States could be crushing.

Perhaps Trump was posturing, for negotiating advantage. Yet not since the days of William McKinley, who engaged in the Spanish-American War in the late 19th century and ended up with U.S. control of the Philippines, Guam and Puerto Rico, has a U.S. president-elect so blatantly threatened the use of force to expand the country’s territorial boundaries.

It was a reminder that Trump’s definition of “America First” is anything but isolationist. He comes to U.S. foreign policy with the mind of a real estate developer, with a penchant for grabbing territory.

He insisted he would not be deterred by the treaty signed with Panama, which was ratified by the Senate in 1978 by a 68-32 vote, just beyond the two-thirds majority required by the Constitution.

He asserted that the return of control of the canal to Panama was a bad idea — arguing that he was reluctant to say so while the nation was burying former President Jimmy Carter, who negotiated the deal. He then returned, repeatedly, to criticizing Carter’s judgment.

“He was a very fine person,” Trump said. “But that was a big mistake.”