Second seed Jelena Jankovic survived yet another testing encounter to reach the quarter-finals of the U.S. tennis Open, beating Danish teenager Caroline Wozniacki in 3 sets.
The Serbian, pushed hard in her previous two matches, again became embroiled in a war of attrition but her superior fitness and strength proved key as she rallied for victory.
The 18-year-old Wozniacki, seeded 21st, out-manoeuvred Jankovic in the first set but as the match wore on the Serbian began to win the majority of the longer rallies.
Jankovic will now play either French 12th seed Marion Bartoli or 29th seed Sybille Bammer of Austria.
Jankovic is one of four players who can overtake compatriot Ana Ivanovic as world number one at the end of the tournament.
