"Italy remaining with just one Grand Prix is unthinkable," the Gazzetta dello Sport newspaper quoted him as saying.
"I am sorry that there are problems when everything seemed to be resolved," he added.
"We are tied to Imola and we will defend it."
Formula One supremo Bernie Ecclestone said earlier in the year that the circuit near Bologna, which is looking for government funding to upgrade the facilities, would be making its final appearance on the calendar this season.
The Formula One championship has already been stretched to an unprecedented 18 races this year and Turkey is due to make its debut in 2005.
The Imola circuit, named after the late Ferrari founder Enzo and his son Dino, is the nearest to Ferrari's Maranello factory and has been on the calendar since 1982.
This year is the 10th anniversary of the death of Brazilian champion Ayrton Senna and Austrian Roland Ratzenberger at the track at the 1994 San Marino Grand Prix.
Michael Schumacher, Ferrari's six-times world champion who won that race and has a better record than any driver at Imola, said this week he would do what he could to keep Imola's hopes alive.
"It's good to come here. Obviously, we all know about the rumours about the future of the San Marino Grand Prix. So, from my side, I hope that they don't come true," he said.
"If I can do anything, then I will try. But I think there is very little in my hands to do."
A banner displayed in the main grandstand opposite the pits on Sunday tried to look on the bright side: "Bernie: Imola...looking forward to seeing you at GP 2005," it said.