French Open chief Guy Forget said on Friday a government order to limit attendance at Roland Garros to a maximum of 1 000 spectators each day was a "tough blow" for the tournament.
Organisers of the French Open, which gets underway four months later than planned in Paris on Sunday, had hoped for a maximum of 5 000.
That figure had already been reduced from 20 000 and then 11 500.
Instead, the French government on Thursday insisted on tougher restrictions to counter the resurgence of the coronavirus.
"We've taken note of the government's decision. We're ready, all the players are here, but it's true it's a tough blow for the tournament," Forget told France Info.
French Prime Minister Jean Castex declared that the Grand Slam tournament must be subject to the same restrictions imposed Thursday on sports events taking place in designated 'red zones' where the coronavirus is showing signs of resurgence.
"We will apply the same rules at Roland Garros as elsewhere," said Castex. "We go from 5 000 to 1 000."
Sources told AFP, however, that the figure does not include credential holders such as officials, media, players and staff.
Earlier Thursday, Forget said he had hoped to protect the 5 000 limit and that the nature of the Roland Garros complex would work in the tournament's favour.
"We are able to accommodate 5 000, as small as it is, on a 12-hectare area," he said.
"We stage the tournament on the equivalent of 15 football fields, outdoors. Everyone wears a mask, even the ball boys and girls and chair umpires."
The limit of 1 000 fans a day represents less than 3% of last year's total attendance of almost 520 000.
There will also be financial repercussions.
In 2019, Roland Garros accounted for around 80% of the French Tennis Federation (FFT) budget - €255.4 million out of a total €325 million.
Ticket sales generate nearly 20% of tournament revenue.
When the planned limit was 11 500 spectators, Forget estimated that "the tournament's proceeds (would) be halved", which corresponded to between 130 and 140 million euros.
The US Open in New York, which ended just under two weeks ago, banned all spectators from its sprawling Flushing Meadows complex.
Wimbledon was cancelled for the first time since World War II.
Murray v Wawrinka blockbuster
Meanwhile, three years after the match which turned out to be the "end of my hip", Andy Murray was handed a Roland Garros rematch against Stan Wawrinka in the pick of first round matches.
In 2017, Murray and 2015 French Open champion Wawrinka fought out a thrilling five-set semi-final which saw the veteran Swiss triumph from two sets to one down.
Murray, 33, has arguably been paying the price ever since with the former world number one battling a long-standing hip injury which at one stage threatened to end his career.
Both Murray and Wawrinka are three-time major winners.
World ranked 111 Murray needed a wild card to play in Paris but will at least be buoyed by a 12-8 winning record over the 35-year-old Wawrinka, the world 17.
World No 1 Novak Djokovic, bidding to win Roland Garros for the second time after his 2016 victory and collect an 18th major, starts against Sweden's Mikael Ymer, ranked 80.
Defending champion Rafael Nadal, seeded two and looking for a 13th French Open crown, begins his campaign against Egor Gerasimov, the 83rd-ranked Belarusian.
Nadal, who is one Slam shy of equalling Roger Federer's all-time record of 20, is scheduled to face third seed and US Open champion Dominic Thiem in the semi-finals.
The 34-year-old Spaniard defeated the Austrian in the last two finals in Paris.
Thiem has an intriguing opener against Marin Cilic, the 2014 US Open winner and a former world number three.
With Federer not taking part, Russia's Daniil Medvedev is Djokovic's scheduled semi-final opponent.
However, Medvedev has never won a match at Roland Garros in three visits.
Defending women's champion and world No 1Ashleigh Barty is skipping this year's French Open over health fears.
Serena v Azarenka in last 16?
Also missing is US Open winner Naomi Osaka through injury.
Simona Halep, the 2018 champion, is top seed and the Romanian starts against Spain's world number 70 Sara Sorribes Tormo.
Serena Williams, a three-time champion in Paris, continues her bid for a record-equalling 24th major.
Williams, who turns 39 on Saturday, begins against compatriot Kristie Ahn who she defeated in the first round of the US Open.
She could face old rival Victoria Azarenka in the last 16, just weeks after the Belarusian won their US Open semi-final.