EMMANUEL DUNAND / AFP - Getty Images

Venus Williams celebrates after her 6-2, 6-1 victory over Mandy Minella at the U.S. Open on Friday.

Ivanovic briefly sat atop the WTA rankings in 2008 after winning that year's French Open, one of three Grand Slam finals she's reached. But injuries and inconsistent play dropped her all the way to 65th in July, and she is currently 40th.

The U.S. Open is the only major tournament at which Ivanovic never has played in the quarterfinals. To change that, she'll need to get past the No. 2-seeded Clijsters, a 6-3, 6-0 winner over No. 27 Petra Kvitova.

"A match like this today probably gives me more satisfaction, because I beat a good player without even playing my best tennis," Clijsters said.

Fifth-seeded Samantha Stosur, sixth-seeded Francesa Schiavone and 12th-seeded Elena Dementieva also advanced.

"It was so strange, because since last evening we all were talking about how bad it's going to be today," Dementieva said. "Coming to the stadium, I was looking at the window, expecting, 'Where is the rain? Where is the wind?' You know, (we were) playing in absolutely perfect conditions this morning."

Stosur, the French Open runner-up, extended her longest run at the Open, beating Sara Errani 6-2, 6-3. She had never gotten past the second round at Flushing Meadows in six previous tries. But the 26-year-old Australian is in the midst of a career year and has reached the quarterfinals or better in nine of her last 10 events.

Stosur beat the 37th-ranked Errani for the second time in just more than a week. She needed a third-set tiebreaker to defeat the Italian in New Haven, Conn.

Stosur nearly lost in the first round at the U.S. Open, dropping the opening set then going to a tiebreaker in the second against 64th-ranked Elena Vesnina. But she has cruised since and had seven aces and 37 winners Friday.

"First rounds are always that little extra bit of nerves and a little tricky," Stosur said. "Vesnina had been playing well recently, so it certainly wasn't the easiest first round you could've got. So to battle through that, I have a chance now to get to this point. And, yeah, I've played quite well the past two matches."

Stosur moves on to face Dementieva, who beat 24th-seeded Daniela Hantuchova 7-5, 6-2. Dementieva, the 2004 runner-up at Flushing Meadows, has reached the semifinals three times but lost in the second round last year. The Russian missed Wimbledon with a left calf injury and has fallen out of the top 10 in the rankings for the first time in more than three years.

Hantuchova has not beaten Dementieva since 2005, not including retirements. The Slovakian reached the fourth round at the U.S. Open last year.

Dementieva converted all six break points Friday. Hantuchova was just three of nine.

French Open champion Schiavone beat 29th-seeded Alona Bondarenko 6-1, 7-5.

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