Tennis-Defending champ Serena Williams reaches quarter-finals

NEW YORK (Reuters) - Two-times defending champion Serena Williams rode her big serve to a 6-3 6-3 victory over Kaia Kanepi of Estonia to advance to the quarter-finals of the U.S. Open on Monday.

Williams won every one of her first serve points in the opening set, including six aces, as she pounded in 63 per cent of them and never faced break point in the set.

The second set saw both players struggle on serve, with a total of six breaks registered, as Williams, who belted eight aces, won with her fourth service break in the final game of the 65-minute match between the ferocious hitters.

"She hits the ball incredibly hard and moves the ball around," said Williams, who hopes to make up for a disappointing grand slam season in which she failed to advance past the fourth round in any of the previous majors. "I just keep fighting."

"I finally made a quarter-final this year!" she shouted to the Arthur Ashe Stadium crowd with arms upraised. "Glad to do it in New York."

Williams will meet Italian 11th seed Flavia Pennetta, a semi-finalist last year who advanced with a 7-5 6-2 win against 29th-seeded Australian Casey Dellacqua.