Cahill, 32, is out of contract at the end of the season and Chelsea are willing to sell this month.
And Ranieri hopes a deal will be done.
"I need somebody who can help us," said Ranieri. "We have a very good team but without experience. We need somebody who has experience, is a leader, has good character, personality and then we can improve our team."
"We have to bring somebody to survive. It would be a very good boost for all of my players.
"We are looking in every direction and we will see what happens. The transfer market is open and we are ready to take something that can help Fulham."