World No 1 Novak Djokovic fought back from a set down to set up a meeting with unseeded Canadian Milos Raonic in the final of the Western & Southern Open in New York.

The Serbian struggled early with an apparent neck complaint against eighth seed Roberto Bautista Agut before finishing 4-6 6-4 7-6 (0) over the Spaniard in three hours and one minute, the longest match of the tournament.

Djokovic described the match to reporters afterwards as "very strange", adding: "I don't know how I won it, to be honest. He was the better player."

The 33-year-old called on his mental toughness and strong serve in the win, serving just three times in the final-set tie-break but with each an ace.

The Serbian, who is also aiming to win his fourth US Open, is one victory away from tying Rafael Nadal for the most Masters 1000 titles with 35.

But to do it he will have to beat former No 3 Raonic after the Canadian upset fourth seed Stefanos Tsitsipas 7-6 (5) 6-3.

Raonic, who conquered Andy Murray on the way to the semi-final, won 90 per cent of first-serve points across one hour and 37 minutes on court.

The 29-year-old, who is ranked 30th, will attempt to become the first unseeded player to lift the trophy in the Open era when he meets Djokovic in the final.

Naomi Osaka, the 2018 US Open champion, will take on former world number one Victoria Azarenka in the women's S&W Open final at 4pm today Irish time.

Meanwhile, the New York Times reported today that Djokovic is trying to form a new body to represent players and has resigned from his position as the president of the players council of the Association of Tennis Professionals,.

Canadian Vasek Pospisil, a member of the Djokovic-led council, said he had also resigned.

"After two years on the ATP Player Council, I am resigning from my position as the player representative for the 51-100 ranking positions," Pospisil wrote on Twitter.

"It has become clear that, as a player council member within the current structure of the ATP, it is very difficult, if not impossible, to have any significant impact on any major decisions made by our tour."

The players are now assembled in New York's bio-secure bubble ahead of the U.S. Open Grand Slam from Monday.

The new body will be called the Professional Tennis Players Association (PTPA) and a document detailing plans and objectives has been distributed to players, seeking their signatures.

"The goal of the PTPA is not to replace the ATP, but to provide players with a self-governance structure that is independent from the ATP and directly responsive to player-members' needs and concerns," the newspaper quoted the document as saying.

The ATP currently governs the men's professional Tour and its board, chaired by former Italian professional player Andrea Gaudenzi, is composed of representatives of both players and tournaments. The body did not respond to request for comment.

Raonic said a "majority" of players was expected to sign in favour of the new association.

"Players have had plenty of time to think and reflect and take a look at certain parts which they may not be happy with and discuss," he said after his win on Friday.

"I don't know. A lot of us were kept in the dark by our leadership for six months. We were disappointed with many things."