Thohir held talks with Moratti in Milan last week over a reported 300 million euros investment in the club, which could see the Indonesian newspaper and communications tycoon acquire a 75 per cent controlling stake at San Siro.
No deal was struck but Thohir has outlined his plans to return to Italy and help Inter become "one of the best 10 teams in the world".
But Pellegrini, who bought the club for 10 billion lire in 1984 before handing the reins to Moratti in 1995, would prefer the Nerazzurri to "stay Italian" rather than "end up in the hands of a stranger".
He told the Gazzetta dello Sport: "The Indonesian is only interested in business. The club must stay Italian and be restructured, I can help find other entrepreneurs.
"I have nothing personal against Thohir, I don't know him and he has an enviable financial position.
"However, this situation saddens me because I would hate to see my favourite team end up in the hands of a stranger."
Thohir, who bought Major League Soccer franchise DC United in 2012, would become only the second foreign owner in Serie A after Roma were bought by an American consortium two years ago.