The Uruguay international had claimed earlier in the week that a move to the Premier League side was close to completion after an £11.8 million bid was reportedly accepted by the Serie A outfit.
However, Guaraldi has warned that the move is further away from finalising than currently being reported.
| MANCHESTER CITY LATEST
|12/1||Manchester City are 12/1 to draw 1-1 with Southampton with bet365
He told Sky Sport 24: “The situation is much more complicated than he thinks. It’s not just about figures, but seeing what is included and what isn’t.”
And the club president went on to claim the bid from Southampton had never been considered and then slammed the player’s agent for his handling of the matter.
“The offer we received has not been considered suitable. His agent has already reached an agreement with the English club, but we haven’t.
“Now the situation is static, we made our demands and will see what happens.
“I don’t understand why Gaston said those things. I won’t even get into the behaviour of his agent.”
The Italian club remain defiant that they will not sell the player unless the €20m (£15.7m) is met, with Guaraldi hinting that interest from a number of other sides had already been rejected.
He continued: “We spoke to the top Italian clubs about Gaston, but I have always been clear: I’d let him go only for a suitable offer, which so far has not arrived. I maintained my consistency and refused the bid.
“I am irritated because one of my players spoke as if he were already at another club, when there still isn’t any agreement.
“I can understand his desire to make the move, but I do not share his timing and methods. All negotiations can collapse, which is why I consider the player’s attitude to be premature.
“The club cannot be forced to follow the rules of players and agents.”
The South American had earlier in the week talked about his excitement at signing for Southampton and shrugged off reports linking him to Inter Milan.
He told Sky Sport Italia: “Inter? There was nothing official. Southampton were the club who decided to sign me and I’m happy that I’ll be going there.”