Australia's Prime Minister has warned Novak Djokovic that he will be on the "next plane home" if his evidence for being exempted from COVID-19 vaccination rules is deemed insufficient. World number one Djokovic is poised to defend his Australian Open title this month after tournament organisers prompted public outrage by granting him permission to play, said dpa international. But the Serbian could yet face problems at the border as the country's government has stated he requires "acceptable proof" that he cannot be vaccinated for medical reasons, with Prime Minister Scott Morrison adamant the player will not receive any preferential treatment on arrival. Djokovic – a nine-time winner – has not spoken publicly about his vaccination status but last year said he was "opposed to vaccination". It remains unclear what qualifies the 34-year-old for exemption, and tournament director Craig Tiley has said it would be "helpful" for Djokovic to clarify his situation. His hopes of competing could yet be scuppered by intervention from the federal government. Prime Minister Morrison told a media conference on Wednesday: "We await his presentation and what evidence he provides us to support that. "If that evidence is insufficient, then he won't be treated any different to anyone else and he'll be on the next plane home. "There should be no special rules for Novak Djokovic at all. None whatsoever." More than 90 per cent of Australia's over-16 population is fully vaccinated. The Australian Open is scheduled to begin on January 17. Tournament director Tiley had earlier revealed 26 unvaccinated players applied for exemption, with Djokovic among only a "handful" given the green light under guidelines set by federal regulators. Having insisted the 20-time grand slam winner had not benefited from "special favour", Tiley later urged the player to be transparent on the issue as public criticism increased. A possible explanation is that Djokovic has contracted coronavirus for a second time at some point in the past six months, having previously caught it during his much-criticised Adria Tour event in Belgrade in 2020. That would negate the need for vaccination, according to rules published last year by one of two independent medical panels involved in the decision. The build-up to the season's first grand slam has been dominated by whether Djokovic would be involved. Speculation was heightened after he pulled out of the Serbia team competing at the ATP Cup in Sydney without explanation. On Tuesday, the 34-year-old Serbian posted on Instagram that he was "heading down under with an exemption permission". The tournament provides Djokovic with another chance to move clear of rivals Roger Federer and Rafael Nadal, with the three having each won 20 grand slam titles. He was challenging for the calendar year grand slam in 2021 but fell short in the US Open final by losing to Daniil Medvedev, the man he beat in last year's Australian Open final. — Agencies