Lionel Messi's father Jorge fears Barcelona will not release him for the Olympic Games next month.
The Catalan club do not want the forward to travel to Beijing as it would rule him out of the preliminary rounds of the Champions League.
FIFA president Sepp Blatter again reiterated on Wednesday that it is 'mandatory' for clubs to release players aged 23 and under for Olympic duty, but a number of clubs, including Barcelona, are lining up to challenge that position and may take the matter to the Court of Arbitration for Sport.
Jorge Messi said on Thursday that his son will be powerless if Barcelona decide to keep him.
'I phoned him yesterday and he wants this problem to be solved. He cannot do anything but wait for the Barcelona directors to say whether he can go or not,' Jorge Messi told the Mananas Informales show in Buenos Aires.
'Two months ago, we talked to Barcelona officials and they were aware of Lionel's aim of playing in the Olympics. The problems started when they said they did not want to release him because they are in the Champions League's preliminary round.'
Brazilian players Diego (Werder Bremen) and Rafinha (Schalke) both left their clubs without permission earlier this week after being called up for the Olympics.
Jorge said his son would not do the same as he believes Barcelona could seek to punish him.
'We have no written rules saying the player should be released. It's just a matter of customs and traditions. I hope Barcelona think about it, change their mind and let him play,' he added.
'As written rules do not exist, Barcelona will fight to retain him, but if Leo flies to Beijing anyway Barcelona can accuse him of abandoning the club.'
Argentina's Under-23 head coach Sergio Batista and the squad are waiting for Messi to join them in Japan, as they are playing the hosts in an exhibition match next Tuesday as warm-up to the Olympics.
The men's football competition will be played from August 7 to 23.