Roger Federer has withdrawn from the upcoming Australian Open as the 20-time grand slam champion continues to work his way back to full fitness following a knee injury, his agent has announced. 

Federer has not played since losing to eventual champion Novak Djokovic in the semi-finals of the 2020 Australian Open at the start of this year, having twice undergone knee surgery since that tournament. 

The 39-year-old Swiss superstar will not travel to Melbourne for the rescheduled 2021 Australian Open, which will take place from February 8-21. 

"Roger has decided not to play the 2021 Australian Open. He has made strong progress in the last couple of months with his knee and his fitness," Tony Godsick said in a statement to The Associated Press. 

"However, after consultation with his team, he decided that the best decision for him in the long run is to return to competitive tennis after the Australian Open. 

"I will start discussions this coming week for tournaments that begin in late February and then start to build a schedule for the rest of the year." 

Federer is a six-time winner of the Australian Open, with his last triumph coming in 2018. 

Ranked fifth on the ATP Tour, Federer had a 5-1 win-loss record before his 2020 campaign was cut short.

The 2021 Australian Open, meanwhile, will take place in February, instead of its typical January 18 start date, amid the coronavirus pandemic. 

There will be warm-up events in Melbourne after travelling players serve 14-day quarantine periods in Victoria that permits them to train for a maximum of five hours per day at a secure facility. 

There will be three ATP warm-up events in Melbourne too, including the ATP Cup from February 1-5. 

The Adelaide International has been relocated to Melbourne and will run alongside an additional ATP 250 tournament in the city from January 31 to February 6.