Argentina superstar Messi agreed terms on a new deal until 2021 last month, with the club saying it would be signed in the near future.

Messi -- who has been at Barcelona since the age of 13 -- has yet to put pen to paper, however, with his current contract ending next summer.

The new terms include an increase in the player's release clause to €300 million.

Speaking during the unveiling of new signing Paulinho, Mestre said: "It's already discussed and agreed.

"Everything seems correct ahead of the signing. We are just waiting to fix a date for the signature."

Asked whether he could offer a "200 percent assurance" that Messi will sign, Mestre said: "Leo's renewal is heading in the right direction. I would be very surprised if it didn't happen."

Mestre had stated he was "200 percent sure" that Neymar would stay at Barcelona a week before the Brazil international joined Paris Saint-Germain in a world-record €222 million move.