Arsene Wenger says "it is now or never" for FIFA to reform the international calendar before they risk a backlash from clubs.
The Arsenal manager is concerned over the demands on the game's biggest stars, with the Frenchman warning that split between clubs and the international game is a realistic prospect, unless FIFA acts to protect the players.
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Wenger said: "We face a situation where it's impossible for the players to get through a season and have rest.
"This kind of friction that it creates between the clubs, national teams and international competitions can create a split.
"One day the clubs could move away and say, 'Enough is enough. We pay a huge amount of money for our best players so we'll get them together ourselves and organize our own competitions'.
"It's important that all of that gets on the table while we have the opportunity.
"It is now or never."
Wenger also believes it is inevitable that the World Cup finals will be expanded to a 40-team competition.
He said: "You see the European Championship has gone from 16 to 24 teams.
"I bet you, because of the way the system was organized to be elected as new president of FIFA, the programme would be to move the World Cup from 32 to 40 teams.
"Why? Because Africa today has five countries in the World Cup and Europe has 13 â that cannot work for much longer.
"You cannot take countries away from Europe [though] and if you want to be elected FIFA president you need the votes from the African countries, so you want to give more to Africa.
"So the next World Cups will be 40 teams."