The Americans did not compete at the 1980 Moscow Games due to a boycott, but they had never been beaten in the men's medley final dating to the inaugural event at the 1960 Rome Games.

"That was a monster split for Pan ... so that's a pretty cool birthday present," said Hunter Armstrong of the US.

Qin, who swam the breaststroke leg in the medley, was also crucial in the victory with a time of 57.98 to beat France's four-gold medal winner Marchand.

Chinese swimmers had been unfairly portrayed in Western media reports about some food-contamination cases, raising doubts over their capabilities. Pan's success came as a timely, powerful response.

Acknowledging that he had been under tremendous pressure, Pan said that he had slept little before the final because of a doping test that ran into the early hours of the morning.

According to World Aquatics, swimming's global governing body, Chinese swimmers were tested on average 21 times from Jan 1 to the start of the Games. In comparison, Australian and American swimmers were tested only four and six times on average, respectively.