COPENHAGEN, Denmark (AP) — President Donald Trump suggested Friday that he may punish countries with tariffs if they don’t back the U.S. controlling Greenland, a message that came as a Congressional delegation met Danish and Greenlandic lawmakers in Copenhagen and sought to lower tensions.

Trump for months has insisted that the U.S. should control Greenland, a semiautonomous territory of NATO ally Denmark, and said earlier this week that anything less than the Arctic island being in U.S. hands would be “unacceptable.”

“I may put a tariff on countries if they don’t go along with Greenland,” he said Friday, without providing details. “We need Greenland for national security.”

He had not previously mentioned using tariffs to try to force the issue.

Earlier this week, the foreign ministers of Denmark and Greenland met in Washington this week with U.S. Vice President JD Vance and Secretary of State Marco Rubio.

That encounter didn’t resolve the deep differences, but did produce an agreement to set up a working group — on whose purpose Denmark and the White House then offered sharply diverging public views. Greenland is a semiautonomous territory of Denmark, a NATO ally of the U.S.