Lionel Messi and Neymar are two of the stars of European football whose participation in the Champions League final, if their side, Barcelona, gets there is in doubt.

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The problem is being presented by this summer's Copa America.

Argentina, Brazil and all the other South American sides will participate in the tournament in Chile, with the start date June 11, which is just five days after the Champions League final in Berlin.

Keeping in mind FIFA want clubs to free up their South American players on May 29, some of Europe's biggest clubs may face a serious problem.

At Barça, it is a particular concern. They face the prospect of seeing Messi, Javier Mascherano, Neymar, Dani Alves and Claudio Bravo all potentially being called up by the countries.

Luis Suarez, too, in the case his ban is lifted, could be called up Uruguay.

National teams have priority over the clubs and want to count on their best players to ensure the best possible preparation takes place before the tournament.

La Liga only ends on May 26, with the Copa del Rey final on May 30, meaning Barça may also lose their stars for the showdown with Athletic Club.

Accordind to Diario AS, FIFA have recommended that Europe's biggest clubs begin negotiating with the South American national teams to ensure they don't lose their South American players if they make it to the Champions League final.