Defending champion Andy Murray crashed out of the US Open on Thursday, after losing his quarter-final clash in straight sets to Switzerland's Stanislas Wawrinka.

The ninth seed Swiss reached his first ever Grand Slam semi-final, with a comfortable 6-4, 6-3, 6-2 win over the British number one at Flushing Meadows. Wawrinka, who has been in good form this season, was dominant from the start, denying Murray so much as a single break point opportunity.

Wawrinka - Murray
Wawrinka (L) beat Murray in straight sets (Reuters)

"It was a tough day for me. He played exceptional tennis and served very, very well. He hit a lot of lines on big points, went for his shots and they all went in today. He played too well. I was playing well enough to get to the quarters. I've played my best tennis at the Slams the last three years. It wasn't maybe my best day today, but the last three years have been great for me and especially the last year," Murray said.

Wawrinka will now play world number one Novak Djokovic on Saturday for a place in the final. The 28-year-old was delighted to get the better of Murray, who won the competition last year.

"Andy Murray's the defending champion, he's a tough opponent. For me to get through in three sets is amazing. It was really windy today. To get that [first] set gave me confidence for the rest of the match. So much was going through my head in the last game. I just try to be focused, to play solidly, aggressively, to take the match and not let him back," Wawrinka stressed.

Second seed, Spaniard Rafael Nadal, will take on eighth seed Richard Gasquet of France in the other semi-final on Saturday.

Meanwhile, in the women's singles semi-final, top seed Serena Williams of USA and fifth seed Li Na of China will face each other, while second seed Victoria Azarenka of Belarus will meet unseeded Flavia Pennetta of Italy.