(Adds Bolt quotes, latest golds, BMX)
* Usain Bolt gunning for unique "double-double"
* Briton becomes first woman Olympic boxing champion
* Ireland's Katie Taylor also boxes to popular gold
* United States catching up with China in medals haul
By Mike Collett-White and Mark Trevelyan
LONDON, Aug 9 Jamaican sprinter and world-record holder Usain Bolt is out to prove that lightning can strike twice on Thursday when he seeks to defend his 200 metres title, while the United States closes in on China at the head of the Olympic medals table.
On the 13th day of competition in London, Briton Nicola Adams became the first woman to win an Olympic boxing title in a thrilling flyweight bout against pre-fight favourite Ren Cancan of China at a packed ExCel arena.
The 29-year-old won easily on points in a four-round blizzard of punches, flooring her opponent once. Minutes later Irish lightweight Katie Taylor followed her to gold, and even louder roars, by narrowly beating Russian Sofiya Ochigava.
All eyes now turn to the athletics track for the big drama of the 200, where Bolt is aiming to become the first man to win both the 100 and 200 at two successive Olympics and be crowned, unofficially at least, the greatest ever sprinter.
The lanky 25-year-old has not shied away from good-natured mind games with his main rival and training partner Yohan Blake, who sprang a surprise by beating him over both distances in the Jamaican trials.
"I told Yohan the 200m will be different because that is my pet event," Bolt said earlier this week. "I'm not going to let him beat me again."
Elsewhere at the main stadium, world decathlon record holder Ashton Eaton of the United States had a comfortable lead over hs compatriot Troy Hardee with just the javelin and 1,500m to come.
Kenyan David Rudisha is clear favourite in the evening's 800m.
World champion Christian Taylor and fellow American Will Claye are likely to battle for triple jump gold.
Women's world record holder and defending champion Barbora Spotakova is one of the world's most consistent javelin throwers but faces stiff competition from Russia's world champion Mariya Abakumova as well as Germany's Christina Obergfoell and South Africa's Sunette Viljoen.
The U.S. women's soccer team will have revenge on their minds when they take on Japan, the side they lost to in last year's World Cup final, in the final at Wembley.
The match is expected to be watched by 83,000 people, breaking the Olympic record for women's soccer and underlining how popular the Games have been with the British public.
Inspired in part by the home team's gold medal haul, the best since 1908, venues have been packed with boisterous crowds, and 80,000 people will again cram the stadium in the evening hoping to witness history.
Two golds on Thursday took Britain's total to 24, five better than Beijing in 2008 and their best performance since 1908, when London first hosted the Games.
In addition to Adams, Charlotte Dujardin won the individual dressage event on her horse Valegro after a freestyle that celebrated British musical classic "Pomp and Circumstance".
Olympic fever has spilled into the Paralympic Games, which run in London from Aug. 29 to Sept. 9. The 2.1 million tickets sold so far have surpassed the previous high for the event of 1.8 million in Beijing in 2008.
The Americans captured seven athletics medals on Wednesday and on Thursday teenager Claressa Shields claimed the women's middleweight boxing title, lifting their haul of golds to 35, just one behind China at the top of the medals table.
On the U.S. team website, the United States stands above China based on medals won. Overall they have 83 to China's 78.
In the 4x400m relay, South African double-amputee Oscar Pistorius was denied the chance to run his team's third leg in qualifying when second-leg runner Ofentse Mogawane collided with Kenya's Vincent Mumo Kiilu, sending both crashing to the ground.
South Africa were given a place in the final on appeal.
Jamaica failed to qualify in the event after Jermaine Gonzales pulled up injured midway through his leg.
Over bumps and around steep banks of the BMX cycling track, there were bone-shaking wipeouts as well as comfortable winners in the men's qualifiers ahead of Friday's final.
Australia's recovery from a slow start to the Games continued on Thursday with gold in the men's K4 1,000m canoeing final on Dorney Lake outside London.
Other winners on the water included Hungary's Danuta Kozak, who added the K1 500m title to her medals cabinet, while Germans Peter Kretschmer and Kurt Kuschela snatched victory in the men's 1,000m canoe pair.
Belgian track cyclist Gijs Van Hoecke was sent home from the Games after photographs appeared in British newspapers of him apparently drunk and being carried into a taxi after a night out in London.
In a doping case dating back to 2004, American time-trial cyclist Tyler Hamilton will officially be stripped of his Athens Olympic gold medal on Friday after he admitted to doping, a source at the International Olympic Committee (IOC) said.
Retired Russian Viatcheslav Ekimov will move up to gold.
Attention began to turn to Sunday's Olympic closing ceremony, which will be titled "A Symphony of British Music" and feature a host of pop stars and some 4,000 local volunteers.
Music director David Arnold, who has devoted much of the last two years to the final act of the London 2012 Games, said he wanted it to be "the greatest after-party in the world".
George Michael, Ed Sheeran and Muse are among the acts who have leaked their participation ahead of time, and the music press is swirling with rumours that everyone from The Who to the Spice Girls, Madness or Adele could join them. (Additional reporting by the Reuters Olympic team)