World number one Novak Djokovic has been entered into the Australian Open despite uncertainty over his Covid vaccination status, while seven-time winner Serena Williams is absent.

Williams, 40, said she was not fit to compete at 2022's first Grand Slam.

"While this is never an easy decision to make, I am not where I need to be physically to compete," she said.

"I will miss seeing the fans, but am excited to return and compete at my highest level."

Great Britain's US Open champion Emma Raducanu, ranked 14th in the world, will make her tournament debut.

Fellow Britons Cameron Norrie, Dan Evans and Heather Watson are also on the entry list.

Twenty-time Grand Slam winner Roger Federer is absent while he continues his rehabilitation from knee surgery, with 2014 winner Stanislas Wawrinka also missing with injury.

The Australian Open begins on 14 January.

Djokovic's father said last month that his son, who has won the Australian Open a record nine times, was unlikely to play at the tournament if a bar remained in place against unvaccinated players.

Tournament organiser Tennis Australia has denied reports that it has explored the possibility of applying for an exemption to Victoria's state rules for 34-year-old Djokovic.

"All players, patrons and staff at the Australian Open have to be vaccinated," Tennis Australia said in a statement.

"Any suggestion that Tennis Australia is seeking 'loopholes' within this process is simply untrue."

The message was reinforced by Victoria's Deputy Premier James Merlino.

"Medical exemptions are just that - it's not a loophole for privileged tennis players," he said.

Djokovic has been named in Serbia's team for the ATP Cup ,which takes place in Sydney from 1 to 9 January.

To play in Sydney without being vaccinated, the New South Wales state government would have to apply for an exemption for him.

Djokovic would then have to do 14 days of quarantine on arrival.