A verbal agreement is already in place with Zarate's current club Al Sadd, and Zarate is expected to move to the Italian capital once the formalities are completed.

Lotito believes the 21-year-old will be even more successful than his Agentinian compatriot Messi, who was runner-up in the 2007 FIFA Player of the Year award.

"We won't announce anything until we have deposited his contract with the authorities," Lotito told Italian sports daily Corriere dello Sport.

"We are used to announcing a new signing only after the contract has been completed and that hasn't happened yet.

"But, save any complications, we are on the right path to signing the player.

"The figures that have been reported by the press don't represent the reality.

"The terms of the agreement foresee a valuation of the player which will rise to around 25million euros because Zarate will turn out better than Lionel Messi."

The complex agreement involves Zarate joining Lazio initially on a loan deal reportedly worth 3m euros, with the club able to buy half the rights to the player before next May for 5.5million. They can then buy the remaining half a year later for 8.5million.

"Certainly it's a significant investment," added Lotito. "But if we're closing the deal it means that we believe in it.

"He is a player who has barely turned 21 and he could represent the future of Lazio."

Zarate enjoyed an impressive loan spell at Birmingham last season and was linked with a move to Portsmouth before opting for Italy.