SERENA WILLIAMS reached her first grand slam quarter-final of the year with victory over Kaia Kanepi at the US Open.

So far there have been none of the wobbles that led to unexpected defeats for the world No.1 in Melbourne, Paris and at Wimbledon.

She has not lost more than three games in any set and was a relatively comfortable 6-3, 6-3 winner over her Estonian opponent.

Williams has looked totally focused on the job in hand this tournament and did not lose a point in her first three service games of the match.

Kanepi, another big hitter, kept pace with her initially, but once Williams made the breakthrough for 5-3, the first set was gone.

Having broken again in the opening game of the second, there was an embarrassing moment for the two-time defending champion when she completely fluffed a smash and dropped her serve to love.

But it was soon forgotten, as was the eighth game when she served for the match and was broken, with Williams clinching victory on Kanepi's serve.

Williams said: "She plays really well, she hits the ball incredibly hard. The turning point was I kept fighting and I relaxed, I said, 'Serena, whatever happens, you're still in doubles'."

The world No.1 then raised her hands in the air, and said triumphantly: "I finally made a quarter-final this year! I think I felt (the pressure) in my serving game, 'Can I please make it to the quarters once this year'. I'm glad to do it in New York."

In the last eight, Williams will face 11th seeded Italian Flavia Pennetta.