By Hugh MacDonald

DEFENDING champion Serena Williams powered her way into the third round with a quickfire victory over Hungary's Melinda Czink.

World No.2 Williams, bidding for a fourth US Open title and 12th grand slam of her career, took just 53 minutes to use her renowned heavy hitting and blast her way past the hapless Czink 6-1, 6-1 under the lights at Arthur Ashe Stadium.

Williams, who will next play Maria Jose Martinez Sanchez of Spain in round three, said: "I think I kept my unforced errors low.

"I definitely made some adjustments. I played her a few weeks ago for the first time so I knew her game better this time. She's a really good player so I was really pumped coming out here and I knew I had to play really good."

In the other quarter of Serena's half of the draw, former champions Kim Clijsters and the champion's sister Venus stayed on course for a last-16 showdown at Flushing Meadow after both coming through their second round ties.

Third seed Williams, the 2000 and 2001 champion, overcame a troublesome left knee to book her place in the third round with a battling straight-sets win over fellow American Bethanie Mattek-Sands.

Belgium's Clijsters continued to show she is a dangerous wild card entry in her comeback year as she knocked out 14th seed Marion Bartoli of France.

Meanwhile, No.12 seed Agnieszka Radwanska of Poland fell prey to Russia's Maria Kirilenko, ranked 59, losing 6-4, 2-6, 6-4.

Also out was France's Amelie Mauresmo, the 17th seed, beaten 6-4, 6-0 by Canada's world No.39 Aleksandra Wozniak.