Reigning champion Kim Clijsters rolled into the US Open quarter-finals on Sunday while third seed Venus Williams booked a date with French Open champion Francesca Schiavone to decide a semi-final spot.

Belgian second seed Clijsters needed only 59 minutes to eliminate Serbian former world number one Ana Ivanovic 6-2, 6-1 for her 18th victory in a row on the Flushing Meadows hardcourts, her 2005 and 2009 titles flanking a hiatus.

Clijsters will next meet French Open runner-up Samantha Stosur, who became the first Australian woman in the US Open quarter-finals since Wendy Turnbull in 1986 by defeating Russian 12th seed Elena Dementieva 6-3, 2-6, 7-6 (7/2).

Fifth seed Stosur saved four match points to win the latest-ending women's match in US Open history at 1.36 in the morning, six minutes beyond the old mark set in 1987 but still 50 minutes off the all-time men's latest Open night.

"It's good to make history I guess," said Stosur, who finished some 14 hours after her next foe. "I've got to recover as best I can and be ready to play tomorrow."

Italian sixth seed Schiavone ousted 20th-seeded Russian teen Anastasia Pavlyuchenkova 6-3, 6-0 in 68 minutes, matching her best US Open showing from 2003 in a year that also saw her win her first Slam in June on Paris clay.

"I feel better than I was at French Open," Schiavone said. "It's very special. I'm very lucky to play so well again in a tournament like this."

Williams downed Israeli 16th seed Shahar Peer 7-6 (7/3), 6-3. The seven-time Grand Slam champion and two-time US Open winner will carry a 7-0 career edge against Schiavone into their matchup.

"Her game is better than ever now," Williams said. "I'm hoping my experience will help me like it did today." Clijsters reached her fifth US Open quarter-final and 17th career Grand Slam quarter-final by quickly adapting to breezy conditions.

"The wind, it's something you can either look at as frustrating or as something that tactically can help you maybe a little bit," she said. "Once I was up 3-1, I felt like I was dictating really well during the points."

Clijsters has 3-0 career edge over Stosur without dropping a set, their most recent meeting coming this year at Miami. Sam is a different player than what she was a few years ago.

She definitely has improved a lot," Clijsters said. "I really have to try and stay focused on opening up the court on the forehand and trying to just go on that backhand."
The only Australian woman to win the US Open title was Margaret Court, who did it five times, most recently in 1973.

Clijsters took the first set in 31 minutes, then broke Ivanovic's first two service games of the second set for a 4-0 edge. The Serb broke back but double faulted away a break and the Belgian held for the victory.

Ivanovic was convinced that Clijsters has what it takes to become the first back-to-back US Open women's champion since Williams in 2001. "She has a really good chance," Ivanovic said. "She's playing really well. She lifts her game when it's a tight situation and she needs it. That's what champions do."

Schiavone used her versatility to win the last seven games and break open a tight match. "I was just focusing on my play," Schiavone said. "It was better because I have spin and Pavlyuchenkova couldn't play so good her backhand, so I tried to play at the best with my rotation."

Williams and Peer each missed on five game points in a marathon 12th game before Peer held to force a tie-breker, but Williams grabbed a 5-1 lead in it and took the first set, then broke three times in the second for the victory.

"Winning the first set always feels good," Williams said. "Instead of regrouping and figuring out how you are going to win the match, you can focus on trying to win it in the second set."