Next year's Kooyong Classic has been cancelled due to COVID-19 restrictions ©Getty Images

The Kooyong Classic, a major Australian Open warm-up event usually played in the weeks leading up to the year's first Grand Slam, has been cancelled due to COVID-19 restrictions.

Running since 1988, the event in Melbourne is the traditional warm-up competition for the Australian Open, with previous winners including Switzerland's Roger Federer and women's world number one and home hero Ashleigh Barty.

Last year's event was held over two simultaneous competitions, with Britain's Dan Evans and Italy's Jannick Sinner winning the men's singles titles and Barty and Belgium's Elise Mertens winning the women's singles titles.

The event was not held in 2020.

Scheduled for next January, Kooyong president Adam Cossar confirmed the event's cancellation due to COVID-19 restrictions, casting further doubt on the Australian Open going ahead.

"We are disappointed having to make this decision but with the great deal of uncertainty over recent months about the arrangements that would be in place in January, it has not been possible to make the necessary plans to deliver the best and safest sporting and hospitality experience for our players, spectators, sponsors, broadcasters, members and event staff," Cossar said in a statement.

Alexander Zverev has been a public sceptic of the COVID-19 vaccine, over which there is some confusion as to whether it is required to compete at the Australian Open ©Getty Images
Alexander Zverev has been a public sceptic of the COVID-19 vaccine, over which there is some confusion as to whether it is required to compete at the Australian Open ©Getty Images

Next year's Australian Open, scheduled for January 17 to 30, is in doubt due to Australia's stringent COVID-19 restrictions, which has seen a vast number of sporting events due to be held in the country cancelled.

The Grand Slam was pushed back by three weeks last year due to the COVID-19 pandemic and was played in front of a reduced crowd, with spectators at one stage banned following a snap lockdown announced across Victoria.

Additionally, players' need to be double-vaccinated to compete in next year's event is currently unclear.

Australia's Immigration Minister Alex Hawke had said anyone visiting the country must be fully inoculated against coronavirus, including tennis players, but an email, issued by the Women’s Tennis Association Player Council, claimed players who had not been fully vaccinated against coronavirus would be allowed to travel to Australia but would need to undergo two weeks of "hard quarantine".

This could prove problematic for some, including Serbia's world number one and defending champion Novak Djokovic, who has refused to discuss his vaccine status, and noted vaccine-sceptic Germany's Alexander Zverev.