UPDATE 1-Tennis-Open-Serena hammers Harkleroad in Paris

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PARIS, May 25 (Reuters) - Fifth seed Serena Williams cruised into the French Open second round amid the evening gloom at Roland Garros after an easy win over fellow American Ashley Harkleroad on Sunday.

Williams, the 2002 champion, was broken in her opening service game but reeled off 12 games out of 13 to win 6-2 6-1 in 76 minutes on Court Suzanne Lenglen.

The 26-year-old, a winner in Bangalore, Miami and Charleston already this year, was rocked on to the back foot in the early stages by the sprightly world number 61 but she soon found her rhythm, clubbing winners from both wings in the fading light.

After pulling off the one-sided win, Williams had an ominous warning for her rivals.

"I feel like I ultimately could have played better," said the former world number one, who is the only former champion in the women's draw.

With Justine Henin's unexpected retirement, Williams has been installed as one of the favourites for the title and she is eager to fulfil that billing.

"I guess I do have pressure now, but I don't put any pressure on myself," she said.

"I woke up and I felt like I have a chance to do really well, so why be nervous now? Just may as well get through it."