The Argentinian Football Association (AFA) announced their squad on Thursday and have included the Barca forward.

But Begiristain admits the club have not given up hope of having him available for the preliminary round of the Champions League.

"Our objective is to go into the preliminaries with all our players, including Messi," he told Spanish sports daily Marca.

"We understand the importance of playing the preliminary round. We think that we are right and the the player should not be freed by us.

"We are in permanent contact with the AFA."

Barca's hopes of succeeding in their efforts to retain their player look slim, however, as Argentina's Olympic coach Sergio Batista is not likely to travel to Beijing without "one of the best players in the world" and a key member of his squad.