Tennis - US Open: Tim Henman reached the quarter-finals of the US Open for the first time in his career as opponent Nicolas Kiefer withdrew in the fifth set of their fourth-round clash with a wrist injury.

Henman, on his 30th birthday, was 3-0 up in the decider after a thrilling match, and will be disappointed to have won the match by default after the pair had brought the best - and worst - out of each other in an entertaining spectacle at Flushing Meadows.

Kiefer won the first set of their fourth-round clash on the tie-break. Henman double-faulted on the first point of the game and his German opponent took the first four games.

Henman broke back twice to take the set into a tie-break but lost it 7-5.

Henman was the first to lose his serve in the second set, but he then fought back to take it comfortably. Kiefer went 3-1 ahead after a tight line call went his way. Henman was clearly upset by the call but fought back to win five games in a row. His first-serve accuracy improved and he took the set 6-3 to level the match.

Kiefer's game was falling apart and Henman stretched his winning run to 10 games in the third set. The German had no answer to Henman's chip and volley tactic and was 5-0 down before registering a game.

The Briton held his serve in the next game to take the set 6-1 to lead 2-1.

Kiefer found his feet to take the first in the fourth set as neither player could break the other's serve. A fortuitous lob by Kiefer cost Henman break point in the fifth game and he went 3-2 down.

The set went to a tie-break at 6-6 and Henman went behind as the German regained his composure following a few outbursts over debatable line calls, going on to win the tie-break 7-5 to take the set and level at 2-2.

The pair looked destined for a battle in the fifth and final set. Henman took a 3-0 lead but play was halted when the German appeared to hurt his right wrist.

Kiefer, following consultation with a trainer, decided to retire, handing Henman his passage to face either Olivier Rochus or Dominik Hrbaty in the quarter-finals.

Top seed Roger Federer also reached the quarter-finals for the first time, without hitting a ball when Andrei Pavel pulled out with an injury. The 16th-seeded Romanian withdrew with a herniated disc.

The Swiss will meet sixth-seeded American Andre Agassi Agassi - who defeated Sargis Sargsian of Armenia 6-3, 6-2, 6-2 - in the quarter-finals tomorrow.

"It happened in the second game of the fifth set against (Hyung-Taik) Lee," said Pavel, referring to his 6-4 6-2 1-6 1-6 6-4 third-round victory on Saturday.

"I felt something on my serve but wanted to win the match and didn't think about it. Afterwards I spoke to the physiotherapist.

"He told me to get something to drink and eat and come back, and when I did that it had got worse and worse.

"There was a very big risk (that) if I played tonight (Monday) it would be much, much worse and endanger my career. I don't want to end my career here like this." Pavel missed two months of the tour in 2003 after suffering a back injury at the Australian Open.

"It's something that I've been working on for a long time, something chronic. But I thought I had it fixed up in a way," he said.

"All I can do is first of all to have no more pain and then try to, at the same time, get somebody to work on my back with the muscles.

"But I'd rather quit tennis than have surgery on my back."