President Donald Trump told NATO Secretary-General Mark Rutte on Thursday that U.S. control of Greenland is necessary to enhance international security, escalating his campaign to annex the strategic Arctic island.

Both Canada and Greenland, which is included in NATO as the territory of founding member Denmark, were raised during an informal press conference in the Oval Office. In the meeting, Trump also applied new pressure on the trans-Atlantic alliance to spend more on its collective defense.

North Atlantic Treaty Organization Secretary General Mark Rutte demurred on Thursday when President Donald Trump baited him into backing his dream of the United States annexing Greenland. Rutte—who has been nicknamed NATO’s “Trump whisperer”—shared laughs with the president throughout their Oval Office meeting on Thursday.