Roger Federer will miss the upcoming U.S. Open after the tennis veteran confirmed Sunday he has decided to undergo a third knee surgery.

The rehabilitation process will rule him out of the sport for many months, he said.

The 40-year-old Swiss, speaking on a video posted to his Instagram account, said doctors told him that in order to feel better he would need surgery and that he hopes the procedure will give him a "glimmer of hope" of returning to action.

"I'll be on crutches for many weeks and then also out of the game for many months," Federer said.

"It's going to be difficult of course in some ways but at the same time I know it's the right thing to do because I want to be healthy and I want to be running around later as well."

Federer, a 20-times Grand Slam singles champion, had two knee surgeries in 2020 which resulted in more than a year of rehabilitation, returning to action in March – 13 months after his Australian Open semifinal exit last year.

He withdrew from the French Open in June after winning his third-round match to save himself for the grasscourt season and a bid to win a record-extending ninth Wimbledon title.

Federer reached the quarterfinals at the All England Club, but lost in straight sets to Poland's Hubert Hurkacz, failing to win a game in the third set.

Federer then withdrew from the Tokyo Olympics as well as a number of lead-up events to the Aug. 30-Sept. 12 U.S. Open.

"I want to give myself a glimmer of hope also to return to the tour in some shape or form," said Federer.

"I am realistic, don't get me wrong, I know how difficult it is at this age right now to do another surgery and try it but look I want to be healthy and I'll go through the rehab process I think also with the goal while I am still active which I think is going to help me during this long period of time."

Toward the end of his 97-second video, Federer thanked his fans for their support. "You guys are always incredible, you always think of me," Federer said.

"Some of you suffer with me, some of you just wish me the best and want to see me back on court or see me smile. I am doing OK so I appreciate that.

"And I’ll update you as I move along with my rehab. I wish you all the best and I’ll check in with you soon."