Flushing Meadows, NY -- (Sports Network) - Second-seeded Jelena Jankovic of Serbia rallied to defeat Danish upstart Caroline Wozniacki in three sets, while fifth-seeded Elena Dementieva cruised to a straight-set victory in her fourth-round matchup Sunday at the U.S. Open.

The former world No. 1 Jankovic struggled badly early before her conditioning took over in the final two frames en route to a 3-6, 6-2, 6-1 victory.

Jankovic will now move on to face Sybille Bammer in the quarterfinals.

Jankovic is the highest women's seed still standing in New York, as her top- ranked countrywoman Ana 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.

Russia's Dementieva, fresh off her gold-medal finish at the 2008 Beijing Olympics, was the only straight-set winner on the women's side, overpowering China's Na Li 6-4, 6-1.

Bammer, meanwhile, overcame 65 unforced errors to top 12th-seeded Marion Bartoli of France. The No. 29 seed Austrian took a first set tiebreaker before badly faltering in the second and recovering for a 7-6 (7-3), 0-6, 6-4 win.

15th-seeded Patty Schnyder also moved on to the quarterfinals, topping No. 28 seed Katarina Srebotnik of Slovenia 4-6, 6-3, 6-3. The Swiss took advantage of Srebotnik's inability to get a first serve in and will now face Dementieva.