AP photo by Dita Alangkara / Roger Federer speaks during a news conference after his Australian Open semifinals loss to Novak Djokovic on Jan. 30 in Melbourne.

LONDON — Roger Federer will miss whatever remains of the coronavirus-impacted 2020 tennis season because of a setback in his recovery from surgery on his right knee.

The record-holding 20-time Grand Slam men's singles champion had arthroscopic surgery on the knee in February and wrote Wednesday on Twitter that he had a second procedure that will delay his return until 2021.

The 38-year-old Federer had initially planned to be sidelined for at least four months, but because the tour was suspended amid the coronavirus pandemic he has barely missed any elite tennis.

"A few weeks ago, having experienced a setback during my initial rehabilitation, I had to have an additional quick arthroscopic procedure on my right knee," Federer wrote. "Now, much like I did leading up to the 2017 season, I plan to take the necessary time to be 100% ready to play at my highest level.

"I will look forward to seeing everyone back on tour at the start of the 2021 season."

Like other sports, tennis has been thrown into disarray because of the COVID-19 pandemic, which has killed more than 400,000 people worldwide.

Wimbledon, the oldest Grand Slam tournament, was canceled for the first time since 1945 — the next edition of the grass court tournament is set to start June 28, 2021 — but organizers of the French Open and the U.S. Open still hope to stage their major tournaments this year.

The start of the French Open was postponed from late May to late September. U.S. Open officials recently said they still hope to hold the tournament as planned in New York. Main draw play is scheduled to begin Aug. 31.

Federer had also planned to represent Switzerland at the Tokyo Olympics, trying to complete a career Golden Slam by winning a gold medal in men's singles, but those Summer Games will now be staged in 2021.

Shortly before his initial surgery in February, Federer reached the semifinals of the Australian Open, where he lost 7-6 (1), 6-4, 6-3 to Novak Djokovic, who went on to repeat as champion.

Said Djokovic later: "Obviously, he was hurting. You could see it in his movement."

Federer, who turns 39 in August, missed much of the 2016 season because of injuries. He returned in 2017 and won the Australian Open and Wimbledon.

Djokovic, who has 17 Grand Slam singles titles, is considering skipping the U.S. Open, if it is held. He told Serbia's state broadcaster RTS on Tuesday that the proposed restrictions because of the coronavirus pandemic would be "extreme" and not "sustainable."