Novak Djokovic is unlikely to play at the Australian Open in January unless COVID-19 vaccination rules are relaxed, according to the player's father.
Organisers recently confirmed that players must be vaccinated against coronavirus to compete in the tournament, which begins on January 17.
World number one Djokovic, who won a record ninth title in Melbourne last year, has not publicly stated whether he has had the jab.
Srdjan Djokovic told Serbia's TV Prva that being vaccinated is a personal choice, and that Tennis Australia's rules are essentially "blackmail".
"As far as vaccines and non-vaccines are concerned, it is the personal right of each of us whether we will be vaccinated or not," he was quoted as saying by news website B92.
"No one has the right to enter into our intimacy, it is guaranteed by the constitution. Everyone has the right to decide on their health.
"Whether [Novak] is vaccinated or not, that is his exclusive right. Will he publish it, I don't think so. I don't know that decision either, and if I did, I wouldn't share it with you. He has the right to decide as he wants."
When asked about Djokovic's decision to play in Australia, his father added: "Whether he will appear there depends on how [the organisers] position themselves. He would want it with all his heart because he's an athlete, and we would love that too.
"Under these blackmails and conditions, he probably won't. I wouldn't do that. And he's my son, so you decide for yourself."
Djokovic, who is tied on 20 major singles titles with Rafael Nadal and Roger Federer, recently said he was unsure of his participation following his appearance at the ATP Finals in Turin.
"I was just waiting to hear what the news is going to be and now that I know we'll just have to wait and see," he said.