The United States set a world record to win the men's 4x100 metres medley relay at the Athens Olympics on Saturday and allow Michael Phelps to match Soviet gymnast Alexander Dityatin's 1980 record for the most medals at one Games.

Phelps, who decided to pull out of the relay final to give team mate Ian Crocker his spot, still benefited from the victory, getting a sixth gold medal by virtue of having competed in the heats.

The United States broke two world records in the race as they collected their 12th title of the Olympics to bring the swimming programme to a rousing close on Saturday.

Aaron Peirsol, double backstroke gold medallist at these Games, gave the U.S. a perfect start, cracking the 100 backstroke world record with a time of 53.45 seconds to beat the mark of 53.60 set by fellow American Lenny Krayzelburg in 1999.

Brendan Hansen held off Japan's Olympic champion Kosuke Kitajima on the breaststroke leg and Crocker increased the U.S. advantage on the butterfly for freestyler Jason Lezak to bring them home in an aggregate time of three minutes 30.68 seconds.

That smashed the 3:31.54 set by the same quartet at the world championships in Barcelona in July last year.

Lars Conrad took Germany past Japan on the freestyle leg for the silver in a European record time of 3:33.62 and Japan took the bronze in an Asian record 3:35.22, ahead of Russia for whom former Olympic champion Alexander Popov made his farewell appearance.

The eighth medal took Phelps past fellow Americans Mark Spitz (1972) and Matt Biondi (1988), who each won seven medals in one Games, to make him the most successful swimmer at a single Olympics.

Phelps had already matched Spitz as the only man to win four individual swimming medals at one Olympics when he beat Crocker by a whisker in the 100 butterfly final on Friday.

Phelps ended the eight-day swimming programme with gold in the 100 and 200 butterfly, the 200 and 400 individual medley, the 4x200 freestyle relay and, having swum in heats though not the final, the 4x100 medley relay.

He also took bronze in the 200 freestyle and 4x100 freestyle relay.

Australia, silver medallists in 2000, failed to make the final when a reserve squad minus Ian Thorpe miscalculated in Friday's heats and were too slow to qualify. Australia finished second in the swimming medals table with seven golds.