ROME (AFP) - World number six Serena Williams pulled out of the WTA Rome International on Friday after hurting her back while training, but thinks she will recover in time for the French Open less than two weeks away, she said.

"I just went for a shot and my back got a little stuck, that's basically how it happened," fifth-seeded Williams, 26, told a news conference.

"I don't expect this to cause any problems in my preparations for the French," which begins on May 25 in Paris, she said.

"I'm in good form, so I'll be going in (to Roland Garros) with a couple of good wins," said Williams, who was to have met French sensation Alize Cornet in the quarter-finals on Friday after winning through to the quarters in two straight-sets matches.

Serena's older sister Venus Williams, seeded seventh, was playing in line a quarter-final match-up with fourth-seeded Serbian Jelena Jankovic on Friday.

Serena Williams' withdrawal removed the possibility of an all-Williams final as the two sisters were on opposite sides of the draw.

Corset now meets Russian sixth seed Anna Chakvetadze, who defeated Bulgarian qualifier Tsvetana Pironkova in three sets earlier Friday.