Gael Monfils was unable to join his girlfriend Elina Svitolina in the semi-finals of the US Open after bowing out in a five-set thriller.

Svitolina reached the last four on Tuesday after defeating Johanna Konta in straight sets, with Monfils watching on.

But the Frenchman, seeded 13, lost a dramatic fifth-set tie-break to Matteo Berrettini.

Italian Berrettini needed five match points to fall over the line, having double-faulted with his first at 5-3 in the fifth.

It became a mental battle with Monfils also double-faulting time after time at the climax of what was the match of the tournament so far.

Monfils took the opening set, but he appeared to tire as Berrettini grew into the contest.

The 24th seed took the next two before Monfils mounted what looked like a final push, converting a fifth break point in a marathon fourth game for a 3-1 lead.

It was hardly a relaxing watch for Svitolina, who has the small matter of a meeting with Serena Williams to prepare for on Thursday.

Monfils somehow took the match to a deciding set but was broken immediately.

Berrettini promptly tightened up on his serve, then broke again and seemed to shrug off a harsh warning for a coaching violation.

But with the winning post in sight, the 23-year-old fluffed his lines, dumping his second serve into the net.

Suddenly Monfils got the jitters with three double faults, two of which gave Berrettini more match points.

But Berrettini dumped both into the net, Monfils somehow surviving to take the match to a tie-break.

Monfils had not served a double fault for the entire second set until that last game, and then a fourth gave Berrettini a mini-break.

To add to the theatre Berrettini challenged a call of out, which was shown to be good, to take a 4-1 lead.

Double fault number five gave Berrettini two serves to win it, but Monfils passed him to haul one mini-break back, and the Italian netted the second.

Berrettini came out on top in a brutal rally to bring up two more match points. He was aced with the first, but when Monfils hit a return long, Berrettini dropped to the floor on the baseline in disbelief.

After picking himself up and staggering to the net, Berrettini said: "Right now I can't remember any points, just the match point – and the double fault!

"I'd like to say congrats to Gael. When I was playing I was thinking it was one of the best matches I had ever seen. I was playing, but I was watching, too. I'm really happy.

"I was pretty lucky I had match points and he didn't have any. It's better to have them. I was a bit tight but you didn't see it.

"I'm really proud of myself. It's a great job for me, my team and my family."

Monfils took the defeat on the chin, knowing he will be at Flushing Meadows for at least one more day regardless.

"I wish I could win, but I love those matches no matter what," he said.

"You know, I'm proud of myself, and, you know, I will be happy to cheer for my girlfriend tomorrow."