MELBOURNE: Tennis superstar Novak Djokovic was Sunday awaiting the verdict on his last-gasp appeal against deportation from Australia over his stance on vaccination, with the judges' decision expected within hours.

After four hours of feisty legal back-and-forth about the Serbian ace's anti-vaccine stance and his alleged risk to public order in Australia, the emergency online hearing adjourned.

Djokovic is fighting to win his release from immigration detention, for his visa to be reinstated and to be allowed to remain in the country to defend his title at the Australian Open, which starts Monday.

"We would hope to be in a position to identify to the parties later in the afternoon what the course is that we propose," Chief Justice James Allsop said.

Djokovic's high-powered legal team painted Australia's effort to deport the 34-year-old as "irrational" and "unreasonable", but at times faced pointed questions from the panel of three justices who will now decide the case.

His lawyer Nick Wood sought to systematically dismantle the government's central argument that Djokovic's anti-vaccine views are a public threat and could cause "civil unrest" unless he is deported.

Despite the Serbian star being unvaccinated, Wood insisted he has not courted anti-vaxxer support and was not associated with the movement.

The government "doesn't know what Mr Djokovic's current views are", Wood insisted.

Djokovic is the Australian Open's top seed. If he retains the title he would become the first men's tennis player in history to win 21 Grand Slams.

But he has spent much of the last week in immigration detention, with his visa twice being revoked by the government over his refusal to get a Covid-19 vaccine before arrival -- a requirement for most visitors.

Government lawyer Stephen Lloyd said the fact that Djokovic was not vaccinated two years into the pandemic and had repeatedly ignored safety measures -- including failing to isolate while Covid-19 positive -- was evidence enough of his anti-vaccine views.

"He has now become an icon for the anti-vaccination groups," Lloyd said. "Rightly or wrongly he is perceived to endorse an anti-vaccination view and his presence here is seen to contribute to that."

In a written submission the government also pointed out that Djokovic chose not to give evidence at the hearing."He could set the record straight if it needed correcting. He has not -- that has important consequences."

'We stand by you'

Because of the format of the court, the justices' decision will be extremely difficult to appeal by either side.

If the Serbian star loses, he will face immediate deportation and a three-year ban from Australia -- dramatically lengthening his odds of winning a championship he has bagged nine times before.

If he wins, he may be released within 30 minutes.

That would set the stage for an audacious title tilt and deal another humiliating blow to Australia's embattled prime minister ahead of elections expected in May.

Scott Morrison's government has tried and failed to remove Djokovic once before -- on the grounds he was unvaccinated and that a recent Covid infection was not sufficient for a medical exemption.

A lower circuit court judge ruled that officials at Melbourne airport made procedural errors when cancelling his visa.

Many Australians -- who have suffered prolonged lockdowns and border restrictions -- believe Djokovic gamed the system to dodge vaccine entry requirements.

Experts say the case has taken on significance beyond the fate of one man who happens to be good at tennis.

"The case is likely to define how tourists, foreign visitors and even Australian citizens view the nation's immigration policies and 'equality before the law' for years to come," said Sanzhuan Guo, a law lecturer at Flinders University.

The case has also been seized on by culture warriors in the roiling debate over vaccines and how to handle the pandemic.

Novak Djokovic's Australia controversy timeline

Australia's immigration minister Alex Hawke has admitted that Djokovic is at "negligible" risk of infecting Australians, but argued his past "disregard" for Covid-19 regulations may pose a risk to public health and encourage people to ignore pandemic rules.

The tennis ace contracted Covid-19 in mid-December and, according to his own account, failed to isolate despite knowing he was positive.

Public records show he attended a stamp unveiling, a youth tennis event, and granted a media interview around the time he got tested and his latest infection was confirmed.

'With or without him'

Djokovic is tied with Roger Federer and Rafael Nadal with 20 Grand Slam titles each.

Spanish great Nadal took a swipe at his rival on Saturday as players complained the scandal was overshadowing the opening Grand Slam of the year.

"The Australian Open is much more important than any player," Nadal told reporters at Melbourne Park.

"The Australian Open will be a great Australian Open with or without him."