Tennis Australia (TA) planned for players and their entourages to arrive in Victoria in mid-December to have time to undertake a mandatory two-week quarantine period before competing in January.
Australia's Victoria state government is confident the Australian Open will go ahead but offered no assurances on Wednesday that players would be allowed to arrive in time for the season-opening ATP Cup and other events in January.
The men's ATP Tour told players on Tuesday that the start of the 2021 season remained up in the air due to "challenges" in Australia, which is effectively closed to international arrivals due to COVID-19 protocols.
Tennis Australia (TA) planned for players and their entourages to arrive in Victoria in mid-December to have time to undertake a mandatory two-week quarantine period before competing in January.
But Victoria premier Daniel Andrews questioned whether players needed to arrive so early and said the government was still working with Tennis Australia on quarantine arrangements.
"(Tennis Australia) are working (with) all of their partners and we're confident that we'll finish up with an Australian Open," Andrews told reporters.
"Whether (players) need to be here in December is the other issue.
"I don't know if that necessarily means there isn’t an Australian Open."
The Australian Open is scheduled to start Jan. 18 at Melbourne Park but dates for the team-based ATP Cup and other events that lead into the year's first Grand Slam have yet to be fixed.
If players are unable to enter Australia until January, they would not be able to play the warmup events unless allowed to while in quarantine, a concession that has not been available to other sports in the country.
The ATP said it was working "as hard as possible" to deliver the calendar of events.
"In discussions with Tennis Australia over the past 24 hours, we have been informed there are some new challenges around the previously planned arrival dates for players and team members," the ATP said in a note to players.
TA declined to comment.
TA boss Craig Tiley told local media this week that the governing body had decided to shift the ATP Cup and all other domestic tournaments to Victoria in January to mitigate the risk of logistical problems arising from COVID-19 protocols.
But Tiley's plans were given short shrift by Andrews, who said his government had not even signed off on the Grand Slam.
Australia has largely brought COVID-19 to heel, with Victoria recording no new cases for nearly three weeks.
But the nation is on high alert after a fresh outbreak in South Australia state in recent days, which prompted authorities to order a six-day lockdown.
World number two Rafael Nadal said arriving later in Australia would not be a "big difference" as long as players could train while in quarantine.
"The only negative thing is we have to be there like 16 days in advance (of competing)," he told reporters at the ATP Finals on Tuesday.
World number one Novak Djokovic said on Monday he was still in the dark as to whether he would be able to lead Serbia's title defence at the ATP Cup.
