Seventh seed Andre Agassi [Images] staved off a stunning fightback from Xavier Malisse to beat the Belgian 6-3, 6-4, 6-7, 4-6, 6-2 on Monday to reach the quarter-finals of the U.S. Open.

The 35-year-old American led by two sets and 5-3 in the third-set tiebreak.

Malisse stormed back to level the match only for Agassi to snatch the fifth and deciding set.

"I came out there striking the ball really well," said Agassi.

"In the third set the standard really picked up. I had my chance at 5-5 in the tiebreak, I went the right way on the return and it just hit the tape, and then in the fourth set he was just too good.

"I was hoping to do something different in the fifth set and it felt great."

Agassi, champion in 1994 and 1999, will play American wild card James Blake or 19th seed Tommy Robredo of Spain in the last eight.

For the best part of three sets Agassi gave Malisse, the world number 54, a lesson in hardcourt tennis as he pulled the Belgian all over Arthur Ashe Court.

But having moved to within two points of the match in the third-set tiebreak, Agassi was left helpless as Malisse hit four winners to take it 7-5.

Malisse, who recovered from two sets down to beat Russian Mikhail Youzhny in the previous round, then outplayed Agassi in all departments to level the match.

However, Agassi broke twice in the fifth set to advance to the quarter-finals for the 13th time.

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