Novak Djokovic is considering missing this year's US Open and instead return to competition on clay ahead of the rescheduled French Open.
The 17-time Grand Slam men's singles champion said the restrictions that would be in place for the Grand Slam tournament in New York, because of the coronavirus pandemic, would be "extreme" and not "sustainable".
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The Serb has voiced concerns over a number of issues which include a 14-day quarantine period required for visitors to the US, a limit of one person per competitor allowed to be present at matches, restricted access to courts and limited ability to move around the city of New York.
"At the moment, the measures are extremely harsh," Novak Djokovic said. "Some of the measures regarding rules and regulations at the US Open and tournaments ahead of the US Open are, for instance, once you land (arrive) at the US territory you must go to quarantine for 14 days.
"For the majority of tennis players, including me, I would not have access to tennis courts and then you would not be able to train.
"This is something that is unthinkable at this moment in time. You would not have access to Manhattan, you would have to sleep in the hotel at the airport. You would have to choose one person who would come to you to the club, there would be no public, no media.
"They are quite extreme conditions for playing. I do not know if that is sustainable.
"Most of the players I have talked to were quite negative on whether they would go there and for me currently, as things stand, most probably the season will continue on clay at the beginning of September.
"Of course, we would all want to go back onto the court as soon as possible, to play tournaments ahead of the US Open and the US Open itself and I hope that it will come to that.
"But there must be some sort of compromise and agreement between the players and the organisers. Whether it will come to that, we will see."
Djokovic's comments come after world No 2 Rafael Nadal said he was not currently prepared to travel abroad for tournaments due to global health fears and quarantine restrictions.
Meanwhile, Roger Federer has already announced he will miss the remainder of the 2020 season after undergoing further surgery on his right knee.
This year's US Open is currently due to run from August 24 to September 13, with the postponed French Open scheduled to start one week later on September 20.
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