Big-spending PSG have made an enquiry to land the Bulgarian as they look to continue reshaping their squad at the Parc Des Princes.
Berbatov's future at United has been the subject of speculation for some time after he slipped out of Ferguson's first-team plans towards the end of last term.
The former Spurs hit-man found himself playing second fiddle to Wayne Rooney and Javier Hernandez at the back end of last season and has seen Danny Welbeck promoted ahead of him to the starting XI this campaign.
It had been suggested United would be prepared to let Berbatov move on with the player entering the final 12 months of his contract at Old Trafford.
However, Leonardo claims Ferguson has warned ambitious PSG off a move for Berbatov before the close of the transfer window as he remains part of his plans at United.
"I had Ferguson on the phone but he told me that he was counting on Berbatov and that he was not for sale," Leonardo told France Football after Sunday's 2-1 win over Valenciennes.