World number one Novak Djokovic has resigned as president of the ATP player council to front a new association aiming to increase the power of the players.
But he faces opposition from Rafael Nadal and Roger Federer, who remain members of the council.
Players wishing to sign up for the Professional Tennis Players' Association were due to meet on Saturday night in New York, where the US Open begins on Monday.
Djokovic first raised the idea of a players' union at the 2018 Australian Open. Since then a number of his peers have been agitating for a greater share of the revenue generated by the Grand Slams, in particular.