All three European club competitions will be expanded to 36 teams from next season. In addition to that, a 32-team FIFA Club World Cup is set to be hosted in the United States next year from June 15th to July 13th.

The International Federation of Professional Footballers (FIFPRO) and the World Leagues Association (WLA) expressed their concern over the expanded competitions in a letter reviewed by BBC Sport and addressed to FIFA President Gianni Infantino and Secretary General Mattias Grafstrom.

The letter said the global football calendar is "beyond saturation" and that national leagues are unable to properly organise their competitions, while players are being pushed beyond their limits, with significant injury risks.

The letter further said the burden "is inherently abusive ... (and) jeopardising national leagues and affecting the health and wellbeing of players."

FIFA did not immediately respond to a request for comment on the letter, and FIFPRO and WLA have not answered a request for further information on their concerns.

FIFPRO and WLA are aiming to discuss their issues before the soccer body's ruling council at the 211-member federation's meeting on May 17th in Bangkok, Thailand.

If FIFA refuses to commit to resolving the issues, FIFPRO and WLA will advise their members of their options, including taking legal action against FIFA, the BBC reported the letter as saying.