The 28 year-old has not played on the ATP Tour since suffering a wrist injury at the grass-court Mallorca Championships in June.

Thiem missed Wimbledon and could not defend his grand slam title at Flushing Meadows, with injury fears lingering ahead of the new season.

Despite not requiring surgery on the damaged wrist, Thiem has been unable to play competitively and experienced a fresh setback this month when he pulled out of the Mubadala World Tennis Championship, an exhibition event in Abu Dhabi.

In announcing that decision on 14 December, Thiem said he was "not yet ready to compete at the highest level", and there was little to inspire confidence when he issued an update confirming he would not travel to play in two events ahead of the Australian Open.

Although Thiem still wants to play at Melbourne Park, where the slam begins on 17 January, his prospects are hinging on him feeling significantly more optimistic about his game and fitness in a matter of days.

"After speaking to my team, we have decided to return to Austria, instead of flying directly to Australia," Thiem wrote. "Unfortunately, I caught a cold [and tested negative for COVID-19] while in Dubai and was unable to practise last week.

"I will therefore not be in the physical condition required to be able to play the ATP Cup and Sydney ATP 250.

"After not competing for the last six months I can't take the risk of coming back too soon and picking up a further injury.

"Overall, the time I spent in Dubai was great as I've increased the intensity and level of practise and my wrist is almost at 100 per cent.

"My aim is still to play the Australian Open but we will make a final decision about my participation by the end of December."