Marin Cilic is confident his ankle injury will hold up for the rest of the US Open after reaching the semi-finals on Tuesday.

The Croatian defending champion hurt his right ankle in his fourth-round win over Jeremy Chardy, but it barely played a part as he overcame Jo-Wilfried Tsonga 6-4 6-4 3-6 6-7 (3-7) 6-4.

Asked about his ankle, Cilic said it was fine - but he was grateful for the rest ahead of his semi-final against world number one Novak Djokovic.

"The ankle is doing OK. I was a bit scared after the match with Chardy, but it's alright," he said.

"It's great to have also two more days until semis, actually three days."

Returning to Flushing Meadows as the defending champion, Cilic has enjoyed another good run in New York.

He said being able to reach the semi-finals left him proud and he feels he has found his rhythm.

"I would say the word pride. I wouldn't pick the word relief in there," Cilic said.

"I came to the tournament knowing that I can play well here, that I just need a few matches to get into the rhythm, and that's what happened.

"I was feeling that I was starting to hit the ball much better. In the previous match with Chardy I finished with the third and fourth set really strongly. I was playing really good tennis.

"Today, to beat Jo with a demanding day like this, it's of course a huge accomplishment."