New York - Five-time champion Roger Federer put on a tennis masterclass on Wednesday, routing Richard Gasquet to reach his 10th US Open semi-final, where he will face close friend Stan Wawrinka.
The 34-year-old, bidding to become the oldest champion in New York in 45 years, took just 87 minutes to beat Gasquet for the 15th time in 17 meetings, his 6-3, 6-3, 6-1 victory only revealing half the story.
The Swiss fired 50 winners and 16 aces and did not face a single break point.
Federer hasn't dropped a set at the tournament in five rounds and has been broken just twice.
But he will be wary of the danger posed by Wawrinka despite holding a 16-3 career edge.
Wawrinka defeated him in their last meeting in straight sets in the quarter-finals on his way to the French Open title in June.
"I faced the big serves of John Isner in the last round so I felt tonight I had a little extra time," said second seed Federer.
"I stayed aggressive and enjoyed myself."
Also enjoying themselves watching the master at work on Arthur Ashe Stadium were Andre Agassi and Bjorn Borg as well as celebrities such as Justin Timberlake and Bradley Cooper.
"Stan played wonderfully against me in Paris and I was happy for him that he won the title. He really deserved it," added Federer, who was playing in his 46th Grand Slam quarter-final to Gasquet's fourth.
"He has worked so hard and really improved. I am happy to play him here for the first time. It's cool for us and Switzerland."
Wawrinka reached the semi-finals with a 6-4, 6-4, 6-0 rout of South Africa's Kevin Anderson.
Wawrinka, the 30-year-old fifth seed, booked a spot in his second US Open last-four match, having also reached the same stage in 2013.
"I played my best match of the tournament so far," said Wawrinka.
"Against Roger, I will need to play my best to win. It's a big challenge but I am ready."
Anderson, the 15th seed and playing in his first Grand Slam quarter-final, had knocked out third seed Andy Murray in the previous round.
That effort seemed to take its toll as he committed 42 unforced errors and carved out just a single break point against the fifth-seeded Wawrinka, who romped to victory in just 107 minutes.
The result shattered 29-year-old Anderson's hopes of becoming the first South African in the semi-finals in New York since Johan Kriek in 1980.
Anderson had won four of his last seven meetings with Wawrinka but he was horribly out of sorts on Wednesday, dropping serve in the seventh game of the first set and ninth of the second.
The third set was all over in 25 minutes with Anderson winning just five points.
"It was really tough out there. (I) was maybe a little bit nervous just with the occasion and a lot of waiting around, switching courts," said Anderson after the match was moved from Ashe to Louis Armstrong Stadium because of worries over rain forecast for the evening.
"Obviously it's something that you deal with, but just getting out there and everything seemed to be going pretty quickly."
US Open results on Wednesday, the 10th day of the 2015 tournament at Flushing Meadows (x denotes seeded player):
Stan Wawrinka (SUI x5) bt Kevin Anderson (RSA x15) 6-4, 6-4, 6-0
Roger Federer (SUI x2) bt Richard Gasquet (FRA x12) 6-3, 6-3, 6-1
Flavia Pennetta (ITA x26) bt Petra Kvitova (CZE x5) 4-6, 6-4, 6-2
Simona Halep (ROM x2) bt Victoria Azarenka (BLR x20) 6-3, 4-6, 6-4
Dominic Inglot/Robert Lindstedt (GBR/SWE) bt Rohan Bopanna/Florin Mergea (IND/ROM x6) 7-6 (7/2), 6-3
Steve Johnson/Sam Querrey (USA/USA) bt Leonardo Mayer/Joao Sousa (POR) 6-3, 6-4
Martina Hingis/Sania Mirza (SUI/IND x1) bt Sara Errani/Flavia Pennetta (ITA/ITA x11) 6-4, 6-1
Anna-Lena Groenefeld/Coco Vandeweghe (GER/USA) bt Caroline Garcia/Katarina Srebotnik (FRA/SLO x5) 7-6 (7/5), 7-5
Casey Dellacqua/Yaroslava Shvedova (AUS/KAZ x4) bt Alla Kudryavtseva/Anatasia Pavlyuchenkova (RUS/RUS x12) 6-2, 2-6, 6-3
Bethanie Mattek-Sands/Sam Querrey (USA) bt Andrea Hlavackova/Lukasz Kubot (POL) 6-4, 6-3
Martina Hingis/Leander Paes (SUI/IND x4) bt Yung-Jan Chan/Rohan Bopanna (TPE/IND x2) 6-2, 7-5