World players' union FIFPRO is to meet with FIFA to discuss its plans to overhaul the international calendar, which include a proposal to hold a World Cup every two years.
A number of high-profile former players such as Brazilian World Cup winner Ronaldo have backed the plans devised by FIFA's head of global development Arsene Wenger, but one current top professional, Wales and Real Madrid star Gareth Bale, has expressed scepticism.
FIFPRO released a statement on Tuesday to say it would not endorse any individual reforms such as shortening the gap between World Cups in isolation without an overarching review of the men's and women's calendar.
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It criticised the level of debate around the subject so far, which it said highlighted "the lack of genuine dialogue and trust between institutions".
UEFA's member associations met on Tuesday, with the match calendar proposals set to be discussed. UEFA president Aleksander Ceferin has already warned his confederation could boycott the World Cup if the plans were voted through.
FIFPRO's statement warned: "Without the agreement of the players, who bring all competitions to life on the pitch, no such reforms will have the required legitimacy."
FIFPRO general secretary Jonas Baer-Hoffmann said: "Players have natural physiological limits and an inherent interest in the sustainable advancement of the game: the success of the sport depends on their physical and mental well-being.
"What we decide at the peak of the game impacts thousands of professionals around the world. Any plans to expand competitions must integrate their collective experience and views.
"It is also once more frustrating that the specific and fundamental impact on the women's game is debated as a side-product rather than its own legitimate process with unique needs and opportunities."
The plans set out by Wenger involve either a World Cup or a continental finals such as the Euros taking place every June.
That would mean the Women's World Cup occupying the same summer as a major men's finals, although it is understood FIFA is considering a July or August slot for the showpiece women's event.
Former United States coach Jill Ellis is leading a parallel calendar consultation in the women's game.