Roger Federer saved precious time and valuable energy as he strolled into the US Open semi-finals with a ruthless win over France's Richard Gasquet.

With rain forecasted for last night and most of today at Flushing Meadows, there was a looming possibility the men's quarter-finals could be delayed, therefore encroaching on the players' recovery time ahead of the semi-finals tomorrow.

Federer, however, took no risks, dispatching Gasquet in just one hour and 27 minutes with a dazzling display under the lights of Arthur Ashe Stadium, which saw the Swiss win 6-3, 6-3, 6-1.

When Federer's father Robert, watching on in the crowd, was asked by ESPN's John McEnroe through his commentary earpiece how many better performances he had seen his son play, the elder Federer signalled zero.

And it would be hard to argue with his assessment of a match which saw the world number two register 16 aces to Gasquet's one, 50 winners to Gasquet's eight and five breaks of serve to Gasquet's none.

McEnroe was on after Federer - playing exhibition doubles with Jim Courier, Michael Chang and Mardy Fish - but it felt like the fun had already started in the final set as Federer experimented with his new rush-return, drop-shots from the baseline and a number of scintillating winners.

"I played a very good match, I felt the ball great from the return - it helped playing John Isner in the previous round and seeing those massive serves," Federer said.

"I felt like I had extra time. I had a good first serve percentage. I was able to stay aggressive and I thought it was a great match.

"This is going to help me to physically and mentally save energy and I hope because of that I can play better in the semi-finals."

Federer will now face Swiss compatriot Stan Wawrinka, who made light work of Andy Murray's conqueror Kevin Anderson, winning 6-4 6-4 6-0 in a brisk one hour and 47 minutes.

The all-Swiss rivalry was for a long time entirely one-sided with Federer stringing 11 wins in a row between 2009 and 2013, but Wawrinka blew away the 17-time major champion in straight sets at the French Open in June, where he went on to lift his second major title.

"Stan played a wonderful match in Paris. I was really happy for him, he went on to win the tournament. He deserved it," Federer said.

"He's been such a great player. He's improved a lot and I couldn't be happier to play him here.

"It's two Swiss in the semis in the US Open, it's very cool for the both of us and I'm looking forward to it."

Wawrinka has gone about his business quietly in New York, efficiently moving through the draw but largely falling short of the excellence he unleashed at Roland Garros.

The fifth seed's display against Anderson, however, hinted at a coming to form at just the right time, as he notched five breaks against one of the most dangerous servers the game currently has to offer.

"For sure it was the best match of the tournament for me," Wawrinka said.

"I was really happy the way I played. I was focused on doing what I wanted in the match.

"I was trying to be really aggressive on the return and make him play a mix or some slice, some aggressive play from the baseline."

Wawrinka even tried out Federer's rush-return himself in what was perhaps an ominous statement of intent to his next opponent.

"Maybe we'll both do only that the whole match," Federer joked. "The longest rally will be about three shots."

ends