Novak Djokovic shrugged off concerns of Rafael Nadal and Roger Federer and announced the formation of a new men's pro tennis players' association that promises to put him on a collision course with his two elite rivals.

Nadal and Federer called for "unity, not separation" after reports their longtime rival was spearheading a breakaway union of tennis professionals.

But after a meeting among players at the conclusion of the Western & Southern Open in New York -- where Nadal and Federer were absent -- Djokovic said the new group was launched.

"After today's successful meeting, we are excited to announce the beginning of the Professional Tennis Players Association (PTPA)," he wrote on Instagram, posting a picture of several dozen players gathered on a tennis court at Flushing Meadows, where the US Open starts on Monday.

"The first player only association in tennis since 1972," he wrote.

Djokovic had acknowledged after his victory over Milos Raonic in Saturday's ATP final that the group was a work in progress.

"We don't have all the answers right now. We are just trying to get a sense of how many players do really want to join this initiative. Then we will take it from there," he said.

He said there was no minimum or maximum target membership, but that he was focusing on reaching out to the top 500 players in singles and top 200 in doubles.

"We're hoping we can get majority of those players. We have to start somewhere," he said.

He said the new organization and the ATP "can co-exist, and should co-exist at the beginning.

"Now, where that's going to take us, time will tell."

World number two Nadal pleaded with Djokovic to rethink a breakaway.

"The world is living a difficult and complicated situation. I personally believe these are times to be calm and work all of us together in the same direction. It is time for unity, not for separation," said the 19-time major winner.

"These are moments where big things can be achieved as long as the world of tennis is united. 

"We all, players, tournaments and governing bodies have to work together. We have a bigger problem and separation and disunion is definitely not the solution."

Federer, a 20-time Slam winner, quickly added his support to Nadal.

"I agree @RafaelNadal," tweeted Federer. "These are uncertain and challenging times, but I believe it's critical for us to stand united as players, and as a sport, to pave the best way forward."

Djokovic said he accepted the position of his "Big Three" rivals but disagrees.

"Of course I would love to have Roger and Rafa on board. Of course I would love to have all the players on board," Djokovic said.

"But I understand. I truly understand that some of them have different opinions and they don't think the time is right. Again, I think the time is right."

- No boycotts, rival tour -
Canadian world number 92 Vasek Pospisil announced Friday that he was quitting the Player Council, saying the post did not provide any chance to influence decisions on the tour.

An ATP statement said, "We recognize the challenges that our members face in today's circumstances, however we strongly believe that now is a time for unity, rather than internal division."

Djokovic hoped to ease tour worries.

"They think that ATP cannot co-exist with the association. I have to respectfully disagree," he said. "Legally we are 100% safe and we are allowed to form the player association.

"This is not a union. This is player association. So we are not calling for boycotts. We are not forming parallel tours."