Tottenham Hotspur have been pursuing the Brazil forward over the past 18 months, but now face competition for his signature from across Europe.
Their Premier League rivals Southampton have recently been credited with an interest, while Italian outfit Napoli are apparently targeting the 23-year-old as a potential replacement for Edinson Cavani.
It has been suggested that an offer in the region of £17m will be enough to tempt Internacional into selling Damiao, but Dunga feels that he is worthy of a higher fee should the club's president opt to cash in on his prize asset.
Dunga told Zero Hora: "I think that offer is too low for Leandro Damiao. He is a goalscorer and a national team player. I have a big hope that he doesn't leave, but I can't guarantee that.
"No manager wants to lose a player as good as Leandro Damiao. He is a striker who imposes himself, who knows how to score goals.
"I am not ready to lose him. You'll have to ask the president if he is ready."
Damiao has been capped 16 times by Brazil, scoring three goals.