Former world champion Ronnie O'Sullivan says allowing fans at the World Snooker Championship is an "unnecessary risk".
Snooker's top tournament is one of a number of sporting events chosen to test the safe return of spectators as part of the easing of coronavirus lockdown rules in England.
The World Championship starts on July 31 and five-time winner O'Sullivan has left open the possibility of withdrawing despite saying he was prepared to take the risk of playing.
With a limited number of fans set to be given access to Sheffield's Crucible arena, O'Sullivan told the BBC: "I just think it's an unnecessary risk. I just don't think you want to be putting people's lives at risk.
"You look at the NHS (National Health Service) and you think this is like a war at the moment and it's those people who have been flat out, and you watch what they go through, and anything to take the stress off them is paramount."
O'Sullivan, who had previously hinted he could pull out if crowds were allowed back into the venue, fired a warning to organisers that he was not certain to keep playing even if he enters the tournament.
"If I get to that point (of feeling uncomfortable), then obviously there is no point in playing. And hopefully I don't, hopefully I feel like I'm there and I'm enjoying it," he said.
O'Sullivan is due to start his first round match on August 2 against a qualifier, as he bids to rebound from last year's stunning opening-round loss to amateur James Cahill.
Ronnie O'Sullivan has issued a warning over allowing fans at the World Snooker Championship