The darling of professional negotiators is to say nothing and let their opposition fill in the gaps. Nervous negotiators’ imaginations take hold; they take silence as a rejection and begin making concessions sua sponte.
After dialog has progressed, one party may stop talking, creating an awkward gap – also see: “Silence” (Field Notes on Top Tactics section)
At some point, the silence must be broken. Ask the silent person an open-ended question. A favorite is, “What are you thinking?”