FIFA president Gianni Infantino's plans to expand the World Cup have run into serious opposition from the organisation which represents Europe's biggest clubs.
Infantino is determined to see more nations playing in FIFA's main money-spinner and has proposed two different formats for both a 40-team and a 48-team tournament from 2026 onwards.
Those options, as well as leaving the competition at its current 32 teams, will be voted on at the next FIFA Council meeting on January 9-10 but Infantino has made it clear that his choice is a 48-team format, with a group stage of 16 three-team groups and then a 32-team knock-out.
But the European Club Association, whose 220 member clubs employ a large number of the players at any World Cup, is against moves to expand the tournament.
In a statement, ECA chairman Karl-Heinz Rummenigge said: "We have to focus on the sport again. Politics and commerce should not be the exclusive priority in football.
"In the interest of the fans and the players, we urge FIFA not to increase the number of World Cup participants."
The statement added that the ECA executive board - whose members include the chief executives of Arsenal, Celtic and Manchester United: Ivan Gazidis, Peter Lawwell and Ed Woodward - has written to Infantino to protest against the idea, citing the "unacceptable" number of games played already by the top players.
FIFA has not responded to the ECA letter yet but may wish to point out that Infantino's preferred format does not increase the number of games the top international sides will play and may even reduce it by one game if those teams fail to advance from the group stage. Semi-finalists will still only play a maximum of seven games, including the final and third/fourth play-off.