Tennis US OpenTim Henman reached the semi-final of the US Open last night - but was again made to work for his victory at Flushing Meadows.

The 30-year-old lost the third set of his quarter-final against Dominik Hrbaty within minutes of the restart of the rain-delayed match but fought back to secure the victory in the fourth.

The number five seed now faces Roger Federer tomorrow in his second Grand Slam semi-final this year - and a win will give him his best chance of a maiden major title.

The British number one's path to the last four of the competition has been drawn out over five games and more than 22 sets, so it was not surprising that this victory was not as straightforward as it could have been.

With a fierce wind affecting his serve, Henman struggled with his toss and was lucky to survive a tense first game on the second day of the clash.

His 26-year-old opponent had another chance to wrap up the set at 6-5 and made no mistake with his second attempt.

But the Slovakian then had no answer to Henman's all-round game and was crushed in a fourth set that will give the Briton confidence.

Henman broke Hrbaty's serve in the first game of the set - and then found his rhythm. He was two breaks up at 3-1 and the Grandstand court were then treated to classic serve-volleying on his way to serving out the set.

A huge second serve also contributed to the 6-1 7-5 5-7 6-2 win.

Henman said: "I'm really pleased. I played well yesterday but came out today hitting the ball hard and not making many unforced errors.

"In these types of conditions it suits my game very well. I decided to come in on everything and see whether he could pass me and that's tough to do.

"It was disappointing to lose the third set but I'm still up 2-1 and in these conditions I got off to a good start in the fourth and stamped my authority and tried to keep the points as short as possible.

"Last night under the lights was very humid and heavy so you can swing away at the back of the court but I needed to finish points off quickly. Both parts of the game were really satisfying."

Henman lost a rain-affected clash against Goran Ivanisevic in 2001 when he led against the Croatian - but had no such problems against Hrbaty.

Federer survived a stirring fightback from twice champion Andre Agassi to reach the semi-finals for the first time squeezing through 6-3 2-6 7-5 3-6 6-3.

Resuming at two sets to one ahead after rain stopped play on Wednesday, Federer was rattled when the 34-year-old Agassi hit back to take the fourth set, breaking serve in the eighth game on a lucky net cord.

But a rare missed forehand from the American in the swirling wind handed the Swiss world number one the crucial break in the eighth game of the final set and Federer held his nerve to claim a place in the last four.

"It was really difficult," Federer said. "It was one of the worst conditions I've played in. It was a good situation for me to be two sets to one up (overnight), but once I lost the fourth set I wasn't very relaxed because I knew Andre was playing very well in the wind. I'm just really happy to get through."

MEN'S SINGLES: Quarter-finals: (5) T Henman (Brit) bt (22) D Hrbaty (Svk) 6-1 5-7 7-5 6-2; (1) Roger Federer (Swi) bt (6) Andre Agassi (USA) 6-3 2-6 7-5 3-6 6-3.

WOMEN'S DOUBLES: Quarter-final: (1) V Ruano Pascual (Spa) and P Suarez (Arg) bt (6) J Husarova (Svk) and C Martinez (Spa) 6-3 6-3.

MEN'S DOUBLES: Semi-final: (3) Mark Knowles (Bah) and Daniel Nestor (Can) bt Julien Benneteau (Fra) and Nicolas Mahut (Fra) 7-6 (7-5) 7-6 (7-5).