Melbourne: Seven-time Grand Slam champion Serena Williams continued her comeback with a stuttering 7-6 (7/4), 6-2 win over Anne Kremer of Luxembourg to reach the Australian Open third round Wednesday.

Williams, who won here in 2003 and 2005,gained momentum as the match went on but failed to dominate Kremer, a 31-year-old qualifier ranked 159 in the world who has only two career titles to the American s 26.

"It was tough to start with, I got off to a slow start and Anne played really well," Williams said.

But Williams, 25,who entered the season-opening Grand Slam unseeded and ranked 81 in the world, said her comeback remained on track amid questions about her physical conditioning .

"I definitely feel I m getting better with each match," she said.

Williams will face a tough test against Russian fifth seed Nadia Petrova in the third round.

She was dumped out of last year s tournament at the same stage by Daniela Hantuchova.

It was the beginning of a frustrating year for Williams, who contested only four tournaments as her career was interrupted by injury and a lengthy court case involving her father and a disgruntled promotion company.

Against Kremer, she struggled to find her range early, making a series of unforced errors that gifted Kremer a service break in the third game.

Her opponent did manage to snatch a break in the fifth game, with Williams appearing troubled by a binding on her foot before changing ends.

The American only just managed to hold her next service game then lifted her intensity to break back and take the next two games without conceding a point.

But Kremer held on and Williams had to fight back from 4-1 down in the tie break to take the first set in 52 minutes.

She regathered to score two early breaks in the final set and race to a 4-0 lead before finally serving out the match after one hour 37 minutes.

While Williams booming serve appeared to be unaffected by her lay-off as she send down seven aces in the first set, she is likely to be concerned at the 33 unforced errors she committed, almost triple Kremer s number.

However, she is not lacking confidence and said after her comfortable first round victory over Italian Mara Santangelo that she felt capable of winning a third Australian Open title.

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