President Donald Trump says Iran has made "a very big mistake" by shooting down an American surveillance drone overnight.
The US says the drone was in international airspace. Iran insists it was over Iranian territory.
Tensions between Iran and the US have intensified since the US accused Iran of attacking a tanker in the Gulf of Oman.
Although Mr Trump seemed to tone down the rhetoric when he spoke to reporters after the downing of the drone was confirmed.
Our correspondent in New York Nick Harper has the details.
