Flushing Meadows, NY -- (Sports Network) - Second seed Jelena Jankovic and fifth seed Elena Dementieva will meet in the semifinals at the U.S. Open after both posted victories on Tuesday.

The Serbian Jankovic, who was ranked No. 1 in the world for one week last month, defeated 29th seed Sybille Bammer of Austria, 6-1, 6-4. Earlier in the day, Olympic gold medalist Dementieva was an easy quarterfinal winner, besting 15th seed Patty Schnyder of Switzerland, 6-2, 6-3.

Jankovic, a semifinalist here two years ago, had just seven winners, but took advantage of 40 unforced errors from Bammer, who was the first mother since Peruvian Laura Arraya Gildemeister at 1991 Wimbledon to reach a Grand Slam singles quarterfinal.

The fifth-seeded Dementieva won her 11th straight match. The Russian moved on in 1 hour, 16 minutes with the help of five service breaks, compared to only one for Schnyder.

The 26-year-old Dementieva is now 10-7 lifetime against the left handed Schnyder, including 2-0 at the U.S. Open, where the Russian prevailed in a fourth-rounder back in 2005.

Dementieva will appear in her fourth U.S. Open semifinal in nine years. She reached the final here in 2004, but lost to fellow Russian Svetlana Kuznetsova.

"It feels much better to win in two sets," said Dementieva. "I remember me being in the final here, but I had such tough matches. It's very tough physically to be ready to play at your best in the final."

The two-time major finalist Dementieva was last month's gold medal winner at the Beijing Games, reached the quarterfinals at the French Open in June, and was a semifinalist at Wimbledon in July.

The other quarters will pit fourth-seeded Serena Williams against seventh- seeded Venus Williams and sixth-seeded Russian Dinara Safina versus 16th- seeded Italian Flavia Pennetta on Wednesday at the USTA Billie Jean King National Tennis Center.

Serena and Venus have advanced to their 24th and 29th Grand Slam singles quarterfinals, respectively. This is the 17th time both sisters have appeared in the quarterfinals of the same Grand Slam event; in a repeat of this year's Wimbledon final, Serena and Venus will take to the court against each other for the 17th time in their careers, with the lifetime head-to-head currently standing at eight wins apiece.