The Bulgarian joined the Ligue 1 side from Fulham in January on a loan deal until the end of the season.
Ranieri has now hinted that the 33-year-old is eager to stay at the Stade Louis II.
"I don't know if he has become number one at Monaco but he is playing, scoring and getting assists," the Italian is quoted as saying by Sky Sports News. "Some show more fighting spirit in challenges but he is working more than before.
"He is important to us and I believe he wants to stay but we will talk about that later."
Berbatov has scored two goals in seven games for Monaco since arriving at the start of the year.