London: Jamaican sprinter Usain Bolt became the first man to retain 100 and 200 titles at the Olympics Thursday by winning the 200-metre heat while the US displaced China from top position in the medal tally with just two days remaining for the Games' conclusion here.
Bolt, who won both the 100 and 200 in world record times in Beijing four years ago, took the 100m gold Sunday and went on to cruise to victory in 200 with a time of 19.32 seconds in front of a capacity crowd at the Olympic Stadium, Xinhua reported.
The 25-year-old then replaced American legend Carl Lewis as the most successful sprinter in history. Lewis had won three golds and a silver in the sprints at the 1984 and 1988 Games.
"I'm now a legend. I'm also the greatest athlete to live," Bolt said. "It was a lot of pressure. It wasn't as easy as I thought it would be, but I came through."
While Chinese diver Chen Ruolin took her country's 200th gold medal at summer Olympic Games from the women's 10m platform.
Chen's gold was China's sixth out of seven in diving at London. They only missed the men's three metres springboard two days ago. It was also China's 200th gold medal at the summer Olympic Games since sharpshooter Xu Haifeng won their first at Los Angeles in 1984.
Chen, 19, also the reigning champion, impressed spectators with her stable performances and collected 422.30 points in total, beating second-placed Australian Brittany Broben by 55.8 points. The bronze went to Pamg Pandelela Rinong of Malaysia.
But that was the day's only gold for China and with 37 golds, 24 silvers and 19 bronzes, they lost the top position on the medal tally to the US, who won five golds Thursday to take their tally to 39.
A lot of hopes of the first ever women's Olympic boxing gold had been pinned on China's world champion Ren Cancan, but she was shocked by Britain's Nicola Adams 16-7 in the women's flyweight category at the ExCel Arena.
American teenager Claressa Shields claimed the women's middleweight boxing title. The Americans went on to win in the men's decathlon and triple jump, women's soccer and water polo.
Ashton Eaton, the world record holder, collected 8,869 points over 10 events for the decathlon title. Eaton's teammate and world champion Trey Hardee claimed silver with 8,671 points and Cuba's Leonel Suarez got bronze with 8,523.
Christian Taylor and Will Claye also finished top two in the men's triple jump, with 17.81 and 17.62 metres respectively.
The US women defeated World Cup champion Japan 2-1 to win the women's soccer gold while their water polo counterparts beat Spain 8-5 for the title.
The US delegation looks set to finish the London Olympics at the top of the medal table since they are favoured to win both men's and women's basketball, women's volleyball outside their traditional territory of track and field.
Elsewhere, Kenya's David Rudisha broke his own 800 metres world record en route to an easy victory, becoming the first man to run under one minute 41 seconds in 1:40.91.
South African 400 metres runner Oscar Pistorius, nicknamed 'Blade Runner' because he runs on carbon fiber prosthetic limbs after having his legs amputated below the knee, was cruelly denied a second chance of running at the London Olympic Games as his teammate Oftense Mogawane crashed to the ground in the second leg of the first 4X400 metres semifinal.
Britain got back to winning track after a day without gold medals Wednesday, taking three from individual dressage (Charlotte Dujardin), women's taekwondo (Jade Jones) and women's boxing (Nicola Adams).
The host is now standing firmly as third place on the medal table with 25 golds 13 silvers and 14 bronzes, followed by Russia on 12-21-23 and South Korea on 12-7-6.