US Open: Roger Federer beats Gael Monfils in five-set thriller

Roger Federer saved two match points as he beat Gael Monfils to keep alive his hopes of an 18th Grand Slam title at the US Open.

The Swiss won 4-6 3-6 6-4 7-5 6-2 in a dramatic New York night session to reach the semi-finals.

Federer, 33, goes on to face Croatia's Marin Cilic in the last four on Saturday.

"I still thought the finish line was far away for Gael," said Federer on falling two sets behind.

"I knew I could play better tennis. When I was down two match points, that's when I wasn't feeling too good any more.

"I thought 'this is it, don't let him have an easy shot, and go down fighting.' But I served well and managed to turn it around."

Monfils had two chances to seal the biggest victory of his career in the fourth set, but saw a backhand float agonisingly long on the first before Federer cracked a brilliant forehand on the second.

Having managed to regain his grip on the match after dropping the third set, a tiring Monfils gifted Federer two double-faults in a row to hand over the following game and his challenge faded fast.

The Frenchman, 28, had enthralled the 22,000 spectators in Arthur Ashe Stadium for three hours, constantly talking to himself, pulling faces and sipping cola at the changeovers.

Federer looked bemused much of the time, and in the early stages made a string of unforced errors as Monfils took the first two sets in little over an hour.

The Swiss berated himself loudly when a chance slipped by in the third set, but he capitalised on his next opportunity with a sharp move to the net and the comeback was on.

A loud "Come on!" followed an early break in the fourth but moments later Federer was angrily swiping at the net and arguing with the umpire after Monfils levelled at 2-2.

When a wild Federer forehand offered up two match points at 5-4, the atmosphere in the stadium was close to delirium, but the 17-time Grand Slam champion went on the attack.

From the brink of defeat, he reeled off five games in a row to take control of the match, all but extinguishing Monfils' hopes of reaching the second major semi-final of his career.

Federer was chasing a remarkable ninth semi-final at Flushing Meadows alone, and he ensured a first return to the last four since 2011 after racing through the final set in 27 minutes.

"It's just unbelievable to win matches like this at Slams," added Federer.

"I have won other big ones in other places but over best-of-five, saving match points against Gael in an atmosphere that it was out here tonight, it's definitely very special.

"I'm not sure I have ever saved match point before in a Slam. If that hasn't happened, I'm unbelievably happy that it was today."