U.S. President Donald Trump meets fellow NATO leaders at a summit on Tuesday as the alliance tries to persuade him that their countries are actively increasing their military capabilities even as the American focus shifts away from its defense of Europe toward Asia.

Trump has been critical of NATO’s abilities to function without American leadership and power, moved to withdraw U.S. troops from Europe and cast doubt on whether the U.S. would come to the aid of a NATO ally under attack. He also remains disappointed at some NATO allies’ refusal to join the Iran war, which he had launched alongside Israel without consulting them.