Record 24-time Grand Slam winner Djokovic co-founded the PTPA in 2020 with Canadian Vasek Pospisil, but he is not among the 12 players as plaintiffs alongside the PTPA.

"In general, I felt like I don't need to sign the letter because I want other players to step up. I've been very active in tennis politics," Djokovic said at the Miami Open on Thursday.

"This is a classic lawsuit, so lawyers to lawyers, type of situation. So to be quite frank with you, there are things that I agree with in the lawsuit, and then there are also things that I don't agree with.

"And I found that maybe some wording was quite strong in there, but I guess the legal team knows what they are doing and what kind of terminology they're supposed to use in order to get the right effect."

Djokovic insisted he does not want to cause a rift in tennis despite his union taking action.

"I've never been a fan and supporter of division in our sport, but I've always fought for better representation and influence of and positioning of the players globally in our sport, which I think is still not where I think it should be and where most of the players think it should be," he added.

"Not just in terms of prize money, but in terms of many other points that have been also stated in that document."

Both the ATP and the WTA Tour have defended their record, pointing to the prize money and security they offer players.

On Wednesday world number three Carlos Alcaraz said he did not support the legal action, partly because he was not informed that he would be quoted in the lawsuit.