tikrit. the iraqi city is under isis control, but iraq's military staging a major offensive to retake tikrit. they are getting a big assist not from the u.s. but from iran. cnn's ian lee is tracking latest from cairo this morning. america is careful about the offensive in tikrit. tell us why. >> reporter: that is right, christine. tikrit is the hometown of iraq's former leader saddam hussein. what we have is a predominately shi'ite fighting force going into a predominately sunni area. you have some arab and sunni tribal fighters with the government. it is the shi'ite militias with the strong ties to iran that a lot of people are worried about. we also know from the semi