Wimbledon PHOTOS: Sublime Serena coasts into third round

Defending champion Serena Williams continued her march towards a sixth Wimbledon title with a straightforward 6-3, 6-2 second-round win over French teenager Caroline Garcia on Thursday.

Top seed Williams won the first set in 30 minutes on No. 1 Court against the 19-year-old Garcia who put up more of a fight than expected on a bright day at the All England Club.

The 31-year-old American, who beat Garcia en route to winning the French Open earlier this month, easily wrapped up victory against the World number 100 to take her unbeaten run to 33 matches.

Williams, a 16-time Grand Slam winner, will next face Japan's 42-year-old Kimiko Date-Krumm.

China's Li Na snapped out of a mid-match meltdown to beat in-form Romanian Simona Halep and reach the third round.

The 31-year-old former French Open champion went through the motions as she surrendered the second set meekly but recovered to win a curious match 6-2,1-6, 6-0 on a muggy Court Three.

Halep, who had won 11 consecutive matches coming into Wimbledon, needed an injury time-out for treatment on her back at the end of the first set and the break seemed to rattle Li who committed a rash of errors in a woeful second set.

With coach Carlos Rodriguez watching on sternly, Li buckled down again and streaked ahead in the decider thanks to some heavy groundstrokes.

The sixth seed, whose best run at Wimbledon was the quarter-finals in 2006 and 2010, will face either Germany's Annika Beck or Czech Klara Zakopalova in the third round.

Giant Argentine Juan Martin Del Potro moved sure-footedly into the third round of Wimbledon with a ruthlessly impressive straight-sets Centre Court win over American-turned Canadian Jesse Levine.

The 6ft 6ins (1.98m) eighth seed, seeking a second grand slam title after his 2009 US Open success, won 6-2, 7-6(7), 6-3 with a display of crushing power but also showed an athletic balance on the lush grass that caused so many problems on Wednesday.

Left-handed outsider Levine was edgy and blown away in the opening set, rallied briefly in an entertaining slug-fest of a second but had no answers in the third as he was overwhelmed by Del Potro's growing weight of shot.

"He's a good fighter and a lefty on grass is tough," said Del Potro. "In the second set I got lucky but by the end I was playing well and my serve was good."

Del Potro, who missed last month's French Open through illness, has spent most of his career shadowing the "big four" and although two of them -- Novak Djokovic and Andy Murray -- could still stand in his way at Wimbledon next week he showed again that he has all the tools to break the cartel.