Four-time defending champion Roger Federer weathered a battle against Luxembourg qualifier Gilles Muller to book his place in the U.S. Open tennis semi-final with a straight sets victory.
The second-seeded Swiss was tested to the full by a player ranked 130th in the world before sealing victory with just one service break.
Federer, seeking his fifth consecutive U.S. Open title but his first grand slam crown of the year, edged Muller 7-5 in the third-set tiebreak to win his 32nd consecutive match at Flushing Meadows.
Federer's opponent in the last four will be either American favourite Andy Roddick or third-seeded Serb Novak Djokovic.
It is Federer's 18th straight Grand Slam semi-final.
