The Professional Tennis Players' Association (PTPA) is seeking a court order to prevent the ATP Tour engaging in "improper, coercive or threatening communications" with players.

The association alleges the ATP has tried to pressure players into signing pre-prepared statements saying they had no prior knowledge of the legal action launched this week by the PTPA.

The union, which was co-founded by 24-time major winner Novak Djokovic, cited "anti-competitive practices and a blatant disregard for player welfare" in lawsuits filed on Tuesday.

Djokovic is not one of the players listed as a plaintiff in the official court documents, but said publicly at the Miami Open on Thursday that there are elements of the lawsuit with which he agrees, and some with which he does not.

The Serb went on to say: "I've seen some changes, but there are some fundamental changes that are still yet to be made and I really hope that all the governing bodies, including PTPA, will come together and solve these issues."

The PTPA, "on behalf of the entire player population", is taking action against the men's ATP Tour, the women's WTA Tour, the International Tennis Federation and the International Tennis Integrity Agency in the US, the UK and the European Union.

Australia's Nick Kyrgios is the most high-profile player to be named as a plaintiff alongside the PTPA.

In papers filed late on Friday to the United States District Court in New York, lawyers for the PTPA asked Judge Margaret Garnett to issue an order which prevents all four defendants from communicating with players about their involvement in the process.

The motion accuses the ATP of threatening to reduce prize money and pension contributions to offset legal fees which it will accrue from fighting the case. It argues this constitutes "flagrant interference" with the jurisdiction of the court.