Argentina forward Lionel Messi [Images] is set to miss the Olympic Games soccer tournament after the Court of Arbitration for Sport (CAS) said his club Barcelona was not obliged to release him.

CAS, meeting in Beijing [Images], upheld an appeal from the Spanish club after FIFA, soccer's world governing body, said clubs must release eligible players for the tournament.

Messi's Olympic prospects now depend on a change of heart from Barcelona who have so far battled hard to stop him playing.

CAS had upheld similar appeals from German clubs Schalke 04 and Werder Bremen regarding the release of Brazilian pair Rafinha and Diego.

But the Brazilians will be able to compete in the Games after the clubs decided to let the players stay in Beijing despite the ruling in their favour.

Argentina remained defiant and coach Sergio Batista said he was hopeful that Messi, one of the biggest names in any sport at the Games, would stay in Shanghai where he has been training with the team ahead of Thursday's game with Ivory Coast.

"I'm calm and confident about this because I have spoken with the player and know what he is thinking. The player is going to make it clear to Barcelona that he wants to stay here," Batista told Spanish media.

 The CAS said that the three European clubs had no legal obligation to release the players for the Olympic tournament.

However, the ruling added: "This decision does not affect the eligibility status of the players who have been validly entered by their National Olympic Committee and who remain fully eligible to compete in the Olympic Games of Beijing 2008.

"In view of FIFA's recommendation made to the clubs to release their players as well as of the Olympic spirit, the CAS call upon the goodwill and good sense of FIFA and the clubs to find a reasonable solution with regard to players who wish to represent their country in the Olympic Games."

"We are confident and hopeful that he will remain here with the team for the whole tournament," Argentina coach Batista told reporters. "I have spoken to him and he says he wants to be here with the rest of the team."

Spanish club Barcelona want Messi to be available for their third qualifying round clash against Beitar Jerusalem or Wisla Krakow with the first leg to be played on Aug 12 or 13.

Before going to CAS, they had previously offered to let him go to the Olympics [Images] after that game, provided they had a comfortable lead for the second leg.

In a statement on their website on Wednesday, Barcelona acknowledged the CAS decision but did not comment. FIFA said they were surprised and disappointed and President Sepp Blatter had appealed to the clubs to let the players take part, despite winning the case.

 "I regret that the CAS has not taken the Olympic spirit into consideration," he said.  The International Olympic Committee (IOC) also expressed disappointment. 

"I am sad for the athletes," the IOC's Olympic Games director Gilbert Felli told reporters. "They are here and dreaming of the Olympic Games. These are some issues between the club and the players and sometimes you can have some difficulties there.