Roger Federer saved two match points to defeat Gael Monfils for a place in the semi-finals of the US Open. Photo by: Mike Segar/Reuters

New York – Roger Federer saved two match points in fourth-set fightback to defeat Gael Monfils 4-6, 3-6, 6-4, 7-5, 6-2 for a place in the semi-finals of the US Open on Thursday.

The heroics from the Swiss second seed - a five time New York champion -sucked the life out of the flamboyant Monfils, who had dominated early on with acrobatic shotmaking in the first two sets which left Federer on the back foot.

But the Swiss, 17-time grand slam champion, showed his elite pedigree as he turned the tables from two sets to love down for the ninth time in his career as he played in his 60th straight grand slam.

In the final two sets, the bloom was off the Monfils game as the Frenchman went down to Federer for the second time in less than a month. Federer owns the series 8-2 as he handed Monfils a first losing set of the tournament.

The black-clad Federer closed it out in just under three and a half hours with a runaway fifth set, serving out the victory with a pair of winners.

Federer will play on Saturday for the final as he takes on Croatian Marin Cilic, who upset Tomas Berdych 6-2, 6-4, 7-6 (7-4) with a powerful serving display featuring 18 aces. Novak Djokovic and Kei Nishkor contest the second semi.

Federer maintained his status as king of the nights on the Ashe showcase court, running his record at the venue to 26-1; he was playing in his 43rd grand slam quarter-final.

The winner admitted it felt great to get through in front of another rowdy after-dark crowd.

“He got off to a good start and when I was down those two match points (tenth game of the fourth set) I wasn't feeling that great.

“I told myself to at least go down fighting, don't miss any easy shots. I served well and stayed in the match,” said Federer.

“Somehow I turned it around (to level and two sets each). I felt great in the fifth and played better as the match went on - it's a great feeling

“I was lucky I guess to some degrees but I went for it. The crowd was unbelievable. It was awesome for both of us.

“Gael put up a great fight; he plays incredible tennis. But I'm glad I got it done,” Federer said after advancing with 43 winners and 44 unforced errors.

“In the fifth I had the moment and was serving huge. Gael's level dropped after a tough fourth set. I was going for every point in the fifth and gave it my all.”

The 18th-ranked Cilic, who at this time a year ago was serving out a six-month ban for a technical infraction of strict anti-doping rules regarding medications, hit 18 aces in his upset win in just under two and a quarter hours.

Victory put the 25-year-old Cilic into a second grand slam semi after Australia four years ago.

The winner, coached by 2001 Wimbledon champion Goran Ivanisevic, finished with a big serve to set up a pair of match points and concluded as Berdych fired a forehand return low into the net.

“It was a truly amazing day for me,” said the winner of two ATP titles this season. “The wind was very gusty but I feel I adjusted better than him.

“It really helped to get the early lead. I could rely on my serve and I also played good tactically - I'm pretty happy with everything.”

Berdych had won five of the pair's eight previous matches but lost to the powerful Croatian in their last meeting at Wimbledon in June. Berdych had been bidding for his second grand slam semi-final of the season after reaching the last four in Melbourne in January.

Cilic is the first from his Balkan country to get this far at Flushing Meadows since Ivanisevic in 1996.

“I've been through some tough times the last few years.” said former top 10 player Cilic. “I'm happy that everything is working out for my team, things have been paying off in the last few months. I'm enjoying my time on the court.

“I'm in the semi-finals and I'm really happy. I'm looking forward to my next match.”

Cilic is contesting his 28th grand slam tournament and stands 61-27 at the majors. – Sapa-dpa