Last year almost all the leading players signed two letters to the four Grand Slam bosses demanding an increase in prize money, payments into a player welfare fund to improve retirement and maternity benefits, as well as involvement in decisions that affected them.
The letters set a target of a 22-percent share in tournament revenue, which would bring the majors in line with the nine combined 1000-level events run by the ATP men's tour and the women's WTA tour.
On Monday, players said in a statement that an announcement by Roland Garros on April 16 of a 9.5 percent prize money rise was not good enough.
It said that last year the French Open generated 395 million euros ($463 mn), a 14-percent increase.
However the total purse went up by just 5.4 percent, reducing player share of revenue to 14.3 percent.
It estimated that this year's revenues would pass 400mn euros, leaving the player cut still below 15 percent.
The letter also complained that Roland Garros was ignoring the other issues raised by players.
"The announcement does nothing to address the structural issues that players have consistently and reasonably raised over the past year," it said.
"There has been no engagement on player welfare and no progress towards establishing a formal mechanism for player consultation within Grand Slam decision making."
While the tours did not release the names of the players who had signed the letters last year, copies of the first, in March, showed that 10 of the 11 top-ranked women had signed.
Sinner, Novak Djokovic, Alexander Zverev and Carlos Alcaraz were among the men who signed - although Djokovic reportedly did not sign the second letter in the summer.
The Serbian has not signed the latest letter either, a spokesperson for the players told AFP.
"For sure it would be great if the Grand Slams wanted to talk to us, because that's how it's supposed to be and I don't really get why there's no more open conversation," Iga Swiatek said at the WTA Finals in November.
Meanwhile, also last March, the breakaway Professional Tennis Players Association (PTPA) which Djokovic founded in 2021 and then quit in January of this year, launched a barrage of lawsuits against almost every other tennis organisation.
In its suit against the US Open organisers, the PTPA pointed out that "in 2024, the US Open made $12.8 million from selling a single speciality cocktail, which was more than it paid to both singles champions combined".
The novelty cocktail, the Honey Deuce, sold for $23 during last year's tournament.
