Roger Federer at Australian Open in Melbourne, Australia, January 30, 2020. (Photos: VCG)

Men's Grand Slam singles record-holder Roger Federer said Wednesday he would be sidelined until 2021 after undergoing keyhole surgery on his right knee. The Swiss said he needed follow-up arthroscopic surgery "a few weeks ago" after undergoing a similar procedure in February.

Federer, whose last Grand Slam win was the 2018 Australian Open, said he "experienced a setback during [his] initial rehabilitation".

"I plan to take the necessary time to be 100 percent ready to play at my highest level," the 38-year-old said in a statement on Twitter.

Roger Federer celebrates after winning an exhibition match against Spain's Rafael Nadal in Cape Town, South Africa, February 7, 2020.

"I will be missing my fans and the tour dearly but, I will look forward to seeing everyone back on tour at the start of the 2021 season."

Following his semi-final loss to eventual champion Novak Djokovic at the Australian Open back in January, the 20-time Grand Slam singles champion hasn't set foot on the tennis court.

The World No.4 was planning to make a comeback at Wimbledon, which was canceled later due to the COVID-19 pandemic.