Serbia's Prime Minister Ana Brnabic said she was neither optimistic or pessimistic as to whether her compatriot Novak Djokovic would be allowed to play in the Australian Open, but hoped for a final decision soon.

Brnabic accepted Djokovic would have violated Serbian public health rules if he attended an event in Belgrade on 17 December having received a positive Covid-19 test result in the previous 24 hours, but added clarification was needed on when the tennis star had received his result.

World number one Djokovic faces the threat of being detained by the federal government for a second time and deported from Australia, despite a court ruling on Monday that quashed an earlier decision to cancel his visa.

"I hope that final decision will be announced soon," Brnabic said. "Uncertainty is not good for any of the stakeholders, neither Djokovic nor the Australian Open."

She said she was "neither optimistic nor pessimistic" as to whether Djokovic will be permitted to stay in Australia, where he would be bidding for a record 21st Grand Slam title.

Brnabic, who spoke to her Australian counterpart Scott Morrison on Monday, said her government was ready to provide guarantees that Djokovic would respect local regulations while in Australia.

Non-residents who are unvaccinated against Covid-19 cannot enter Australia unless they are exempted. Djokovic, who is not vaccinated, based his exemption on contracting the virus last month.

The government argued his exemption case was inadequate, but the court overturned that decision.

Asked about Djokovic's attending a Belgrade Tennis Association event on 17 December, the day after he tested positive, Brnabic said the star would have "clearly violated the rules" had he known of the test result before he participated.

However, additional clarification was needed. "I don't know when he received the test result, when he read it," Brnabic said.