Organisers have trumpeted that 18 of the world's top 20 players will take part in the 16-nation tournament in Sydney from January 1-9, with Djokovic leading the top-seeded Serbians.

Djokovic hadn't publicly committed to defending his Australian Open title at Melbourne Park or revealed his vaccination status, with a mandate that he be double-jabbed to play.

While the ATP Cup doesn't have the same entry criteria, his inclusion for the Open warm-up tournament means he now appears likely to chase a 10th crown.

To play without being vaccinated in Sydney, the NSW government would have to apply for an exemption for Djokovic and the 34-year-old would have to undergo 14 days quarantine upon arrival.

Australia has been included in pool B alongside defending champions Russia, and strong squads from Italy and Austria.

The Australians will be led by Alex de Minaur, along with James Duckworth, Max Purcell, John Peers and Luke Saville.

The Russians will be spearheaded by world No.2 Daniil Medvedev as well as Andrey Rublev, Aslan Karatsev, Roman Safiullin and Evgeny Donskoy.

Serbia will start favourites in Group A, which will also feature Norway, Chile and Spain, although world No.6 Rafael Nadal hasn't been included in the latter's line-up.

A winner of 20 grand slam titles alongside Djokovic and Roger Federer, Nadal is still expected to contest the Australian Open, starting on January 17.

The nine-day event will be played in Sydney at Ken Rosewall Arena and Qudos Bank Arena.

Australian Associated Press