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.

American control of the Arctic island is necessary to enhance international security, the US president says in meeting with NATO chief.

He's been dubbed the "Trump whisperer," but NATO general secretary Mark Rutte struggled to get a word in Thursday as the US president mused about annexing Greenland and criticised allies over defence spending.