Williamses arrange quarterfinal match

NEW YORK -- By now, Venus and Serena Williams know all too well how it feels to set aside sisterhood for a couple of hours and try to beat each other on a tennis court.

They know what it feels like to meet at a Grand Slam tournament, what it feels like to win such a match, what it feels like to lose.

And they much prefer it when there's a major championship at stake. The all-Williams showdown, set up by their easy victories Monday at the U.S. Open, comes earlier this time.

This time, Williams vs. Williams is only a quarterfinal.

"It's so soon," Serena said. "You know, it's just disappointing to be so soon."

Both advanced through the fourth round without a challenge. The No. 7-seeded Venus dismissed No. 9 Agnieszka Radwanska of Poland 6-1, 6-3, before No. 4 Serena dispatched wild-card entrant Severine Bremond of France 6-2, 6-2 at night.

Of the eight women left in the tournament, only two have won a Grand Slam title -- Serena leads all active players with eight, and Venus is right behind with seven.

Also advancing Monday were No. 6 Dinara Safina, who defeated Anna-Lena Groenefeld 7-5, 6-0, and No. 16 Flavia Pennetta, who beat No. 32 Amelie Mauresmo 6-3, 6-0.

In men's action, No. 1 Rafael Nadal held off 55th-ranked Sam Querrey, a 20-year-old Californian who never before had been to the fourth round at a major tournament. Querrey hung in during extended baseline rallies, and even briefly led in the third set, before losing 6-2, 5-7, 7-6 (2), 6-3.

Also advancing: No. 17 Juan Martin del Potro of Argentina, who ended the run of Kei Nishikori, the first Japanese man to reach the U.S. Open's fourth round in the 40-year Open era. Del Potro won the contest between teenagers 6-3, 6-4, 6-3 for his 23rd consecutive victory.

Del Potro will face No. 6 Andy Murray, who beat 10th-seeded Stanislas Wawrinka 6-1, 6-3, 6-3.

Fish serve-and-volleyed his way past No. 32 Gael Monfils in straight sets. As for facing Nadal?

"I feel like a guy with my style of play is someone that he doesn't want to see," said Fish, who won the point of 45 of 69 trips to the net. "You've got to be able to finish points quickly. He's going to last longer than anybody. He wants to keep the points as long as possible and run the guys down, kind of body-blow after body-blow."

Nadal has won 42 of his past 43 matches.