Novak Djokovic has been named in Serbia's team for January's ATP Cup in Sydney despite uncertainty over his vaccination status.
The 34-year-old world number one has yet to reveal whether he has been vaccinated against Covid-19.
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.
The record nine-time Australian Open champion has yet to commit to defend his title in Melbourne after organisers confirmed that all players would need to be vaccinated.