LONDON: Defending champion Serena Williams moved into the semi-finals at Wimbledon with a 7-5, 6-3 win over Chinese ninth seed Li Na on Tuesday.

Williams claimed a last four place at the All England Club for the seventh time in her career and helped heal Williams` family pride after older sister Venus was knocked out earlier in the day by Bulgaria`s Tsvetana Pironkova.

Li was completely outplayed by the American top seed as her game unravelled on Centre Court and she never looked likely to emulate her achievement of reaching the semi-finals of the Australian Open.

Yet the Chinese number one, who rallied briefly in the second set, can look back with satisfaction after equalling her best performance here when she reached the quarter-finals in 2006.

Service dominated in the first set, although Li was having to fight the harder of the two to hold hers.

Li saved two break points in the fifth game and finally buckled in the 11th game of the first set when she fluffed two simple forehands and gifted the game to Williams, who served out for a 1-0 advantage.

Li was exasperated with herself for netting a simple volley in the second set and gestured to her coach in the crowd.

But Serena stepped up a gear. She broke Li in the fifth game of the second set and held her serve for a 4-2 lead.

The writing was on the wall for Li when she imploded in her next service game.

She should have challenged a first serve call when TV replays showed the ball was in and ended up double faulting to hand Williams the game.

Li then broke Williams to give herself a lifeline but was only delaying the inevitable and could not hold her own serve to stay in the match.

Serena remains on course for her fourth Wimbledon singles title, while Li`s exit means that Asian hopes of singles glory rest with Lu Yen-Hsun - who is due to play Novak Djokovic in the men`s quarter-finals on Wednesday.

BDST: 2235hrs, June 29, 2010