Serena beats Pennetta, faces Clijsters in semis

NEW YORK (Reuters) - Champion Serena Williams won a war of heavy groundstroke rallies to beat battling Italian Flavia Pennetta 6-4 6-3 on Tuesday and set up a semi-final clash against former winner Kim Clijsters at the U.S. Open.

Second-seeded Williams overpowered Pennetta to break serve at love in the 10th game for the first set, and then earned the only other break of the hard-fought match in the sixth game of the second set to clinch victory.

The final point typified the hard-hitting match, with Williams sealing victory at the end of a long, blistering rally with a bullet forehand passing shot up the line.

"She never gives up, is such a great player and never gave up tonight," the American, who has yet to lose a set in the tournament, said in an on-court interview after the 75-minute victory.

"I thought it was a real good match."

Tenth seed Pennetta, who saved six match points in her fourth-round victory over Russian Vera Zvonareva, slugged it out from the baseline against Williams but in the end the American was just too powerful.

"She was playing really well," said 27-year-old Pennetta, who has been playing her best tennis this year. "She was really aggressive. The ball was very heavy for me tonight.

"She was playing really great, really aggressive. When you play with this player, you cannot make mistakes. Today I make a few mistakes on important points.

"I give everything on the court tonight. I was like running and fighting until the end. It's the only way to win against this kind of player. I was there but tonight was not my night."

Williams, 27, was dominant in her service games, sending seven aces past Pennetta and knocking in 86 percent of her first deliveries.

The victory lifted Williams to a semi-final showdown against Clijsters, who has come back to competitive tennis after leaving the circuit for more than two years to start a family.

Williams has won seven of eight career meetings with Clijsters. The first time they met was in the third round of the 1999 U.S. Open, which Williams won en route to her first grand slam singles triumph.

"Now it's like a totally different level, because she has absolutely nothing to lose. I think that's when you can play your ultimate best tennis," the 11-times major champion said.

(Editing by Pritha Sarkar)