US President Donald Trump has claimed victory at the NATO summit, saying progress had been made on defence spending only hours after throwing the Brussels meeting intodisarray with fresh attacks on European allies.

Asked whether he had threatened to pull out of NATO, Trump did not directly deny it. He told a surprise press conference before he was scheduled to leave that he only told people he would be "extremely unhappy" if spending was not increased. Trump claimed he could pull the US out of NATO without the approval of Congress. "I think I probably can but that's unnecessary," he said.