Nadal reaches semi-finals Us Open 2008

The world No1 has not looked quite at his best since arriving here from his Olympic gold medal triumph in Beijing and was a set down against the American but with typical gutsy resolution he ground out a 3-6, 6-1, 6-4, 6-2 victory.

When Murray met Nadal at Wimbledon in the quarter-finals this summer he found the Spaniard just too good for him – for a fifth consecutive time. But since then Murray's game has moved up a notch and he will be looking to expose chinks in Nadal's armour, just as Fish did initially.

In Saturday's semi-finals, Nadal will face British sixth seed Andy Murray, who reached his first Grand Slam final with a 7-6 (7/2), 7-6 (7/1), 4-6, 7-5 victory over Argentina's 19-year-old Juan Martin Del Potro.

"It's going to be very difficult. I'm going to have to play my best," Nadal said. "He's coming with big confidence. He's doing very well. I expect a very tough match."

Saturday's other semi-final pairing will be decided later Thursday when four-time defending champion Federer meets Luxembourg qualifier Gilles Muller and Serbian third seed Novak Djokovic faces US eighth seed Andy Roddick.

Nadal could match Rod Laver, Pete Sampras and Roger Federer as the only men to win three Slam titles in a row in the 40-year Open era. The only Spaniard to win the US Open was Manuel Orantes in 1975, when the event was played on clay.

Nadal, 22, has won an ATP-best 41 hardcourt matches this year and seeks his ninth title of the season. He has won 54 of his past 56 matches, losing only to Juan Carlos Ferrero at Rome and Novak Djokovic at Cincinnati.