WASHINGTON (AFP) - Two Chinese fighter jets passed dangerously close to an American spy plane in international airspace over the Yellow Sea, a US official said on Tuesday (Sept 23).

News of the close encounter came as Chinese President Xi Jinping began a state visit to the United States.

The incident occurred on Sept 15 when the Chinese planes intercepted an American RC-135 reconnaissance aircraft and crossed directly in front of it, the official said, speaking on condition of anonymity.

Pentagon press secretary Peter Cook declined to give specifics about what happened but confirmed an incident had taken place.

"The pilot reported that he felt like the aircraft passed in front of his nose in an unsafe fashion," Mr Cook told reporters.