FIFA has ordered clubs to release Under-23 players who receive call-ups for London 2012's Olympic Games football tournament, reports SportsPro. The competition clashes with European clubs' pre-season preparations and FIFA's order could prove controversial as the event is not deemed part of the international match calendar.

The football tournament for Beijing's 2008 Olympics was marred by a dispute between Barcelona and Argentina over the participation of Lionel Messi.

The dispute went to the Court of Arbitration for Sport (CAS), which ruled in Barcelona's favour only for the Catalan club to relent and grant permission for Messi to compete.

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