NEW YORK -- Top seed Roger Federer survived a stirring fightback from twice champion Andre Agassi to reach the semi-finals of the U.S. Open 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 out there," Federer said. "It was one of the worst conditions I've ever 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."
The 23-year-old Swiss is trying to become the first man since Mats Wilander of Sweden to capture three Grand Slams in the same year.
He won three of the past five Grand Slams but this is the Grand Slam that has given him the most trouble, losing in the fourth round in each of the last three years.
"It is my first time in the semis so I hope I can keep it up," Federer said. "Three out of four (Grand Slams) would also be fantastic."
Agassi said the wind was not an excuse but the gusts made it difficult for him to get into a rhythm.
"Hitting the ball in the centre of the court was a great shot today," Agassi said. "I just didn't come up with it when I needed it. It was as extreme as it gets. If chairs are blowing over that is a problem."
Federer will now play fifth seed Tim Henman, who became only the second British man in the Open Era, after Greg Rusedski in 1997, to reach the last four when he beat 22nd seed Dominik Hrbaty 6-1 7-5 5-7 6-2.
Henman came tantalisingly close to victory on Wednesday night, cruising to a two-set lead when rain returned to halt his smooth progress.
He held serve at 4-5 in the third when play resumed on Thursday but two games later a netted approach shot gave Hrbaty the set and a glimmer of hope.
However, the 30-year-old, who had never gone beyond the fourth round at Flushing Meadows before this year, quickly regained control, breaking the Slovakian twice to set up a meeting with Federer.
Henman's progress is all the more impressive because he began the tournament hampered by a lower back injury that threatened his involvement.
The four-times Wimbledon semi-finalist, yet to reach a grand slam final, then survived five-set marathons against giant Croat Ivo Karlovic, Czech Michal Tabara and Nicolas Kiefer.
In previous meetings with Federer, Henman holds a healthy 6-2 head-to-head lead, although the Swiss won their last meeting on hardcourts at Indian Wells this year.
