Justine Henin-Hardenne and Elena Dementieva survived plucky fight-backs before reaching the last 16 at the U.S. Open on Saturday.

French Open champion Henin-Hardenne, the seventh seed, took the first nine games of her 6-0, 7-6 third round win over South Korean Cho Yoon-jeong.

Cho, though, suddenly came to life and forced a tiebreak with some punishing groundstrokes before Henin-Hardenne restored order, winning it 7-4.

"I took a step back on the court," conceded the Belgian, who was the champion at Flushing Meadows in 2003. "She took her opportunities and put me under a lot of pressure."

Henin-Hardenne plays either France's [Images] Mary Pierce, whom she thrashed in the French Open final in June, or Serbia and Montenegro's Jelena Jankovic in the last 16.

Sixth seed Dementieva, who was runner-up last year, flirted with defeat in her 6-1, 4-6, 7-6 victory over fellow Russian battler Anna Chakvetadze [Images].

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As usual, Dementieva's game was infested with double-faults -- she served 19 in total -- but her experience told eventually against 18-year-old Chakvetadze who finished in tears after losing the tiebreak 7-5.

Two alluring men's third round matches were taking place later on Saturday, with Spanish second seed Rafael Nadal [Images] facing in-form U.S. player James Blake.

That match on Arthur Ashe Court was due to be followed by the clash between 35-year-old U.S. seventh seed Andre Agassi [Images] and dangerous Czech teenager Tomas Berdych.

Chile's Olympic champion Nicolas Massu reached a grand slam fourth round for the first time when he thrashed Switzerland's [Images] Stanislas Wawrinka 6-4, 6-3, 6-0.

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