U.S. President-elect Donald Trump does not take office until Jan. 20, but on the world stage he is already acting as if he is U.S. president.

Trump has stamped his seal on U.S. diplomacy on crises in Syria and Ukraine as his second spell in the White House approaches.

World leaders have jostled to talk to Trump and he was treated as the guest of honor at the grand reopening of the Notre-Dame cathedral in Paris on the weekend.