Mary Pierce avenged the most painful defeat of her career when she surprised Belgian seventh seed Justine Henin-Hardenne 6-3, 6-4 in the fourth round of the US Open on Monday.

Three months ago the 30-year-old Frenchwoman sobbed uncontrollably after collapsing 6-1, 6-1 to the Belgian in the French Open final but on Monday a wide grin replaced the tears under the glistening lights on Arthur Ashe Court.

Plagued by double-faults, 2003 champion Henin-Hardenne looked a shadow of her usual self and Pierce controlled her fragile temperament sufficiently to set up an all-French quarter-final with third seed Amelie Mauresmo.

Resilience was the by-word on Labor Day at Flushing Meadows.

U.S. seventh seed Andre Agassi [Images] and number eight Guillermo Coria of Argentina came through five-setters and wild card James Blake recovered from a set and 5-2 down to win.

Pierce's nerve has failed her so often in the past but never as badly as in Paris, when she apologised to the crowd for her abject display.

On Monday, though, she ripped into a 5-0 lead with some clubbed forehands and despite some customary wobbles towards the end, drew the decisive error out of the under-par Belgian on her fourth match point.

It was her first win in five meetings with 23-year-old Henin-Hardenne and she said: "I just gave everything I had tonight, I fought and I didn't give up."

U.S. seventh seed Agassi delved into his 20 years of experience at Flushing Meadows and plucked out a 6-3, 6-4 6-7, 4-6, 6-2 victory over belligerent Belgian Xavier Malisse.

It was hard work for the 35-year-old twice former champion who reached the quarter-finals for the fifth straight year.

"I knew it was on the bubble of getting really tough," said Agassi, who nonetheless added that his back injury had not caused him any problems.

In the last eight he will face compatriot Blake, who recovered superbly to upset Spanish 19th seed Tommy Robredo 4-6, 7-5, 6-2, 6-3.

IDOL AGASSI

Agassi is Blake's idol and the 25-year-old, who shocked Spanish second seed Rafael Nadal [Images] in round three, finds himself in uncharted territory after reach his first grand slam quarter-final.

"I don't think I'll nervous because I know I have nothing to lose," said Blake. "(Losing to) Andre Agassi in the quarter-finals of the U.S. Open, I'm sure as heck not going to go home and say I had a bad tournament."

Coria also showed great resilience to win a bad-tempered five-set encounter with Nicolas Massu of Chile.

The two were involved in heated verbal exchanges on Louis Armstrong Court before the Argentine eventually prevailed 6-4, 2-6, 6-7, 6-2, 6-2 in over four and a half hours to reach the quarter-finals for the second time in three years.

Olympic champion Massu was infuriated after Coria requested treatment for damaged toenails. Coria later described the incident as a "misunderstanding."

He will face either French teenager Richard Gasquet or unseeded American Robby Ginepri in the last eight. They were due to play in Monday's second evening session match.

In contrast to the men, women's second and third seeds, Lindsay Davenport [Images] and Amelie Mauresmo, enjoyed a holiday stroll into the quarter-finals.

Davenport thrashed Nathalie Dechy of France [Images] 6-0, 6-3.

The 29-year-old American was severely tested by Dechy in the Australian Open semi-finals this year before winning in three sets but there was never any prospect of a repeat on Monday.

"Today was the best match I've played since Wimbledon," said Davenport, who lost in the longest final on record at the All England [Images] Club to compatriot Venus Williams [Images] in July.

"It's the kind of tennis I want to play. I was consistent, hitting the ball hard. I'm very excited about that."

In the quarter-finals Davenport, the 1998 champion, faces Elena Dementieva, the Russian with the dodgy serve who was runner-up last year.

Dementieva beat Switzerland's [Images] Patty Schnyder 6-4, 6-3 to avenge her fourth round defeat by the same player at the same stage of this year's Australian Open.

Mauresmo, the 2002 semi-finalist, was a 6-1, 6-4 winner over Russian 19th seed Elena Likhovtseva.

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