American swimmer Michael Phelps [Images] became the most successful Olympian of all time when he won his 10th gold medal on Wednesday and his fourth of the Beijing [Images] Games.

The mighty Phelps broke his own world record to continue his dominance in the Water Cube pool and overtake an elite group including Mark Spitz [Images] and Carl Lewis [Images] who had won nine golds.

- Day 4 at the Games | Images

The 23-year-old showed little apparent emotion after winning the men's 200 metre butterfly in 1.52.03, knocking six hundredths of a second off his world record. Each of his four medals in Beijing have come in world best times.

Phelps is now halfway to surpassing Spitz's record of seven golds in one games.

He could add another gold to his tally later in the morning when he races in the men's 200 metres freestyle relay, an event the Americans traditionally claim as their own.

Another highlight of the day will come in gymnastics where China and the United States, already fighting an epic battle at the top of the medals table, face each other in one of the Games' blue riband events, the women's team artistic gymnastics.

But strong performances in the pool grabbed the early attention. France's [Images] Alain Bernard broke the world record in the 100 metres freestyle semi-finals but lost it less than five minutes later to Australia's [Images] Eamon Sullivan.

Italy's [Images] Federica Pellegrini broke the women's 200m freestyle record in a victory that partly made up for losing in her favourite race, the 400 freestyle.

Phelps's triumph pushed him ahead of compatriots Lewis and Spitz, "Flying Finn" distance runner Paavo Nurmi [Images] and Soviet gymnast Larysa Latynina [Images] on nine golds.

Latynina and fellow Soviet gymnast Nikolai Andrianov hold the record for the most career medals of any colour, with 18 for women and 15 for men respectively.

US-CHINA BATTLE

Americans might have brushed China aside in a basketball match earlier in the week, but they are so far trailing the hosts 13 golds to eight in the medals table.

Few contests will be as closely watched as the women's team gymnastics. The Americans, who dethroned the Chinese as world champions in 2007, had arrived with high hopes of giving their country their first Games team title on foreign soil.

But two of their gymnasts, Chellsie Memmel and Samantha Peszek, are both nursing ankle injuries and they were outclassed in qualifying.

Their best hope is that the Chinese fail to cope with an unaccustomed early start, after the event was switched to the morning to catch the prime-time American television market. Some faced wake-up calls as early as 6 a.m..

"I'm tense about it because I'll be lying awake worrying about it all night," said Chinese gymnast Cheng Fei. "I'll be very tired in the morning."

China's men grabbed gold in their gymnastics team event on Tuesday, sparking national rejoicing after returning home from Athens in 2004 without a medal.

The road cyclists will be thankful that Beijing's weather has improved for Wednesday's time trial between two sections of the Great Wall. The women race one lap of the 23.8km circuit, while the men race two.

Suffocating heat and smog forced a third of the field in the men's road race to abandon their bikes on Saturday, while a day later thunderstorms and chill rain left the women cyclists to face treacherously slippery conditions.