MELBOURNE (AFP) - Tennis chiefs insisted America's Tennys Sandgren was not a coronavirus risk after he sparked a flurry of concern by tweeting that he had boarded a flight for the Australian Open in Melbourne despite testing positive.

The world No. 50 is among more than 1,200 players and support staff arriving in Australia from Thursday (Jan 14) for 14 days' quarantine ahead of the delayed Grand Slam, which is due to start on Feb 8.

Sandgren sent out a series of tweets before his departure from Los Angeles, initially saying he had tested positive on Monday and would miss his flight. It was his second positive result, having originally been diagnosed with Covid-19 in November.

But an hour later he said: "Wow I'm on the plane. Maybe I just held my breath too long. Craig Tiley is a wizard."

Tiley, the Australian Open tournament director, has spent months trying to deal with the logistical nightmares of hosting the Grand Slam during a pandemic.

Tennis Australia said players were only allowed into Australia with proof of a negative Covid-19 test prior to departure, or with approval as a recovered case at the discretion of the Australian government.

"In the case of Tennys Sandgren, who has self-disclosed that he previously tested positive in late November, his medical file had to be reviewed by Victorian health authorities," it said. "Upon completion of that review, he was cleared to fly."

But in a country that largely has the coronavirus under control, it caused jitters on social media where Sandgren was a top trending topic. Melbourne only emerged from months of lockdown in October.

"We're nervous enough about tennis players flying in & being irresponsible - please don't joke about this," tweeted one person.

Another added: "Imagine ruining an international tournament and putting a country of millions at risk for Tennys Sandgren."

Sandgren later tweeted to clarify: "My two tests were less than (eight) weeks (apart). I was sick in November, totally healthy now. There's not a single documented case where I would be contagious at this point. Totally recovered!"

'Tested again and again'

Players are due to touch down in Melbourne on chartered planes from seven cities, although the game's biggest stars, including Novak Djokovic, Rafael Nadal and Serena Williams, will arrive in Adelaide and quarantine there.

They will have to stay in their hotel rooms for 19 hours a day, allowed out only to practise and train for five hours in strict bio-secure bubbles.

On Wednesday, Tiley insisted the risks were not high.

"Every one of these players will be coming into Australia into a 14-day quarantine program," he told Australia's Channel Nine.

"They'll all be tested prior to getting on a plane on flights that we are administering, there's no one else on those flights.

"When they arrive they will be tested again and again before they can move into a modified (quarantine) programme."

Two players - America's Denis Kudla and Argentinian Francisco Cerundolo - tested positive for the virus during Australian Open qualifying in Doha this week.

Despite the quarantine, Tiley said he expected virtually all the top players to make the trip with a handful of exceptions, including injured Swiss great Roger Federer and world No. 25 John Isner, who pulled out over the Covid-19 restrictions.