President Donald Trump on Wednesday reminded Europe he is willing to withdraw U.S. troops protecting the region if it doesn’t back him on the “little things,” including supporting the war in Iran and U.S. control of Greenland. 

Trump made the comments on Air Force One as he flew back to Washington from the “quite nice” NATO summit he attended with other world leaders this week in Turkey. The president praised “tremendous unity and togetherness” at the meeting but criticized some allies for not backing his agenda, a move he said could cost them defense support from the United States. The U.S. has already pulled back its military presence in Germany and Poland, stoking concern on the continent.