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 Barcelona are desperate to keep hold of the 21-year-old forward for the preliminary round of the Champions League, set to be played on either August 12 or 13.

Though Bundesliga clubs Schalke and Werder Bremen have taken the issue to the Court of Arbitration for Sport, Barcelona have said they hope to negotiate with the AFA to find a solution with which all parties are happy.

But Grondona insists he will not accept Messi joining the Olympic team with the Beijing tournament already under way.

"I talked on Saturday with (Barca president) Joan Laporta and I let him know that the rules are on our side," he told Clarin newspaper.

"Now, I don't have anything to talk with them about.

"Until now we haven't had any answer from Barcelona. We have asked for him and we have let FIFA know that the player wasn't released on time.

"There is no chance of Messi joining the team with the tournament already started. It's simple - they release him or they don't.

"And if he doesn't come I want to stress that I am not going to take any action against Messi."

Meanwhile, Argentina legend Diego Maradona has accused Messi of lacking character over the issue.

He told Fox Sport Latin America: "I think that Messi lacks of a bit of character. I pray to god that he can earn that through his football.

"I wish he could change his temperament. I can't imagine him fighting for prizes or saying something to a partner. I don't see him like that yet. I hope that in two or three years we can say that Leo is a real leader."

The 1986 world champion believes the Barca youngster needs to stand up to his club.

"The Catalonians are very stubborn and they are not going to let him go just like that," he said.

"But I believe Barcelona have to know there is a country behind this decision and a gold medal is in jeopardy.

"He has to decide for himself. This is a chance to grow as a man. He should say to the Barcelona board that he's leaving.

"He has to go to the Olympic Games and stay calm. Not for nothing did they give him the number 10 shirt and treated him the way they have."