American military chiefs have been left dumbstruck by an undetected Chinese submarine popping up at the heart of a recent Pacific exercise and close to the vast U.S.S. Kitty Hawk - a 1,000ft supercarrier with 4,500 personnel on board.

By the time it surfaced the 160ft Song Class diesel-electric attack submarine is understood to have sailed within viable range for launching torpedoes or missiles at the carrier.

According to senior Nato officials the incident caused consternation in the U.S. Navy.

The Americans had no idea China's fast-growing submarine fleet had reached such a level of sophistication, or that it posed such a threat.

Chinese sub pops up in middle of U.S. Navy exercise, leaving military chiefs red-faced