US Open: Kei Nishikori beats Novak Djokovic in the semi-finals

Kei Nishikori, of Japan, celebrates after defeating Novak Djokovic

Kei Nishikori stunned world number one Novak Djokovic at the US Open to become Japan's first Grand Slam singles finalist.

The 10th seed won 6-4 1-6 7-6 (7-4) 6-3 and will take on Marin Cilic for the title on Monday after the Croat shocked Roger Federer in straight sets.

Nishikori, 24, coached by Michael Chang, responded superbly after losing the second set to seal his biggest win.

"It's just an amazing feeling, beating the number one player," said Nishikori.

"I hope it's big news in Japan. I feel the support from Japan. It's 4 o'clock in the morning but I hope a lot of people are watching."

Nishikori had needed 10 sets and more than eight hours to win his previous two matches, but produced a remarkable performance as temperatures hit 36C and humidity soared.

"It was really tough conditions today, it felt a little bit heavy and humid," he added. "I guess I like long matches."

Few expected Nishikori, making his Grand Slam semi-final debut, to have the stamina to test Djokovic after his epic wins over Milos Raonic and Stan Wawrinka in previous rounds.

The Japanese player made the better start though, breaking twice to take the first set against a strangely flat Djokovic, who beat Britain's Andy Murray in a gruelling quarter-final.

It was still no surprise when the Serb, playing in his 24th major semi-final, raced through the second set in half an hour as Nishikori appeared to finally be flagging.

A dramatic third game early in the third set proved pivotal, though, as Nishikori survived four break points and seven deuces to hang on, bringing the crowd on side as they got behind the underdog.

Flashing backhand and forehand winners had Djokovic reeling as Nishikori broke for 5-3, but a nervous service game followed and he double-faulted when trying to close out the set.

Again, it appeared that Djokovic would finally assume control and power on to a fifth straight US final, but the top seed continued to struggle and played a poor tie-break.

A wayward forehand on set point was his sixth unforced error in 11 points and the prospect of a major shock became very real when he then dropped serve at the start of the fourth set.

The frustrated Serb screamed in the direction of his coach Boris Becker, while the German's former on-court rival Chang clenched his fists as he willed on Nishikori in the opposite corner.

There was one more test for Nishikori to negotiate but, just as he had done over the course of three dramatic matches, he played his way out of trouble from 0-40 to move 2-0 up, and Djokovic would not get another chance.

Another searing backhand return brought up two match points and Djokovic's challenge ended with a tired forehand over the baseline.

"Other than that second set my game today was not even close to what I wanted it to be," said Djokovic.

"A lot of unforced errors, a lot of short balls. I just wasn't myself."

Both players suffered in the intense heat and humidity at Arthur Ashe Stadium

Kei Nishikori jumped for joy after clinching his famous victory over the seven-time Grand Slam champion

Coach Michael Chang has played a key role in helping Nishikori reach his first Grand Slam final