Flushing Meadows, NY -- (Sports Network) - Former world No. 1 Jelena Jankovic and Olympic gold medalist Elena Dementieva were a pair of third-round victors Friday at the 2008 U.S. Open.

The second-seeded Jankovic snuck past gritty Chinese Jie Zheng 7-5, 7-5 at Ashe Stadium, as the hard-hitting Serb needed 2 hours, 10 minutes to advance.

Jankovic prevailed in a wild 12th game in the second set on Day 5, as she needed five match points in an 18-minute game that went to deuce 11 times and saw Zheng enjoy seven break-point chances.

The 23-year-old Jankovic converted on her fifth match point when Zheng netted one final weak forehand.

Zheng was a surprise Wimbledon semifinalist last month. She shocked French Open champion Ana Ivanovic in the third round at the storied All England Club.

Jankovic is the highest women's seed still standing in New York, as her top- ranked countrywoman Ivanovic was a shocking second-round loser against French qualifier Julie Coin here on Thursday.

The popular Jankovic, a U.S. Open semifinalist in 2006 and quarterfinalist here last year, was ranked No. 1 for just one week two weeks ago.

Jankovic will meet the Victoria Azarenka-Caroline Wozniacki winner in the fourth round this weekend. Wozniacki was last week's surprise hardcourt titlist in New Haven.

Meanwhile, a fifth-seeded Dementieva, of Russia, drove out Britain's Anne Keothavong 6-3, 6-4. The two-time major runner-up Dementieva reached the U.S. Open final four years ago and captured Olympic gold in Beijing earlier this month.

Up next for Dementieva will be Chinese Na Li, who got past Russian Ekaterina Makarova 6-1, 4-6, 6-2.