Josep Maria Bartomeu says Lionel Messi's father has already signed the forward's new Barcelona contract, which means the new deal is already valid.
Barca announced in July that Messi had agreed to renew until 2021, after his previous agreement was due to expire in 2018.
The club said at the time that formal signing of the contract would take place in the "coming weeks", but two months have passed since without the Camp Nou icon putting pen to paper, prompting speculation of a shock transfer, with Pep Guardiola's Manchester City among the sides linked.
But president Bartomeu claims the renewal is already valid after the player's dad Jorge signed and is optimistic the photocall for Messi's deal will happen within a month.
"It's all agreed and signed," Bartomeu told Sport.
"There are three contracts. One with the Messi Foundation, which is signed with the president of the Foundations and the player's brother.
"There's an image rights contract with Messi, which his father has signed, who is the administrator of his company, and the employment contract, which his father has signed, who has the power to do so."
Asked what was still lacking, Bartomeu explained: "That Leo arrives and we have the official photograph and the protocol of the signature.
"The contract's signed, it's valid from the month of June, from June 30, the same day that he got married, curiously.
"It's been audited because it goes into the accounts for last season. The renewal is included in the accounts for the closing of this season. There are no problems. It's just the protocol of the signature. We're relaxed."
Bartomeu acknowledged that "scheduling problems" had not been ideal, but urged Barca fans not to worry.
"We've had schedule problems," he said. "Now, he's back on September 6 or 7, then we play on September 9. There are a lot of games. We will find the moment.
"Two months have gone by. He got married on June 30, then when he came back he went to Japan, then there was the tour. Then he came back – ah - what happened? There was the Supercopa, then LaLiga started, the trip to Monaco.
"We will find the moment. I hope so [within a month].
"People shouldn't be [worried]. There's been a lot of noise but they can be calm."
Bartomeu disagrees with observers who feel Messi looks sad on the pitch this season, verdicts that have fuelled speculation over his contract status.
"I don't see that," he said. "Focused, yes, very. I saw him the other day on the trip to the UEFA event. He was relaxed, happy.
"We speak regularly with the players. They are all happy."
Messi, who turned 30 in June, has spent his entire senior career with Barcelona and made his debut in 2004.
In an astonishing career, he has won LaLiga eight times and the Champions League on four occasions, among a total of 29 club trophies.
