Warned of legal action over their plans for the 2025 Club World Cup, FIFA said Thursday they would guarantee player welfare in a harmonious schedule.

FIFA is however facing the threat of legal action from domestic leagues and player unions if there is no rescheduling of the 2025 Club World Cup.

A letter to FIFA president Gianni Infantino, seen by AFP, claims the sport's worldwide schedule is now "beyond saturation".

FIFA were swift to react.

"The FCWC tournament dates (15 June – 13 July) have been set to ensure that the scheduling of the tournament is harmoniously aligned with the IMC to allow sufficient time between the tournament final and the start of the season in many domestic leagues globally, and considering that a minimum of three days of rest between matches should be guaranteed in order to safeguard player welfare," a FIFA statement said.

The original letter sent by the World Leagues' Association (WLA) and FIFPRO, the international players' union, which include the Premier League and England's Professional Footballers' Association among their respective memberships warns changes are needed.

These include the new 32-team Club World Cup -- scheduled to take place in the United States in June and July 2025 -- have created "economic harm" to domestic leagues and pushed players "beyond their limits".

The letter urges FIFA's ruling council to reschedule the Club World Cup and re-open talks on the international calendar for the years up to 2030.

"Should FIFA refuse to formally commit to resolving the issues, as set out above, at its upcoming council, we shall be compelled to advise our members on the options available to them, both individually and collectively, to proactively safeguard their interests," the letter said.

"These options include legal action against FIFA, on which we have now commissioned external expert advice."

The football schedule will already expand next season, with the Champions League and Europa League to have eight first phase games compared to six this term.

The Champions League, Europa League and UEFA Conference League will all be increased to 36 teams.

WLA and FIFPRO accused world football's governing body of "continually and consistently making unilateral decisions that benefit its own competitions and commercial interests, while negatively affecting national leagues and players".

They added: "Over a significant period, FIFA has ignored repeated attempts by leagues and unions to engage on this issue.

"Leagues and players cannot simply be expected to 'adapt' to FIFA's decisions, which are driven by FIFA's business strategy. We have reached the point where this situation must immediately be addressed both from a procedural and substantive perspective."

Premier League chief executive Richard Masters said last month: "It is getting to a tipping point. The feedback we have from players is that there is too much football being played and there is constant expansion.

"The Premier League hasn't changed shape. What has changed over the last few decades is the march of international and regional football competitions.

"It stands to reason if you overload the calendar and the players, at some point, something has to give."