Then ask for the offer. Some candidates talk so much during interviews that they talk themselves out of a job they've already landed. Or worse, they keep selling after they've made the sale. Then they're dead. Listen and give the interviewer a chance to hire you.
Silence is an amazingly powerful tool in closing.
If you don't say anything, the interviewer may feel compelled to fill the void and tell you something vital. Do this discretely. Too many silences can be awkward. Pace yourself with the interviewer. Try these closes.