In 1969, United Nations Command negotiator and US Maj. Gen. James B. Kapp and North Korean Maj. Gen. Ri Choon-Sun sat across the table from one another for 11.5 hours without eating or using the restroom. The delegates were only permitted to leave the room if the person who called the meeting proposes a recess. Ri never did. In fact, the two men spent the last 4.5 hours of the meeting silently staring at one another. At 10:30pm, Ri stood up and walked out.
During the meeting, Knapp had asked Ri for North Korea to begin a four-step process to calm tensions in the region.
The infamous meeting was featured in Jeffrey Z Rubin and Bert R. Brown's book "The Social Psychology of Bargaining and Negotiation" which sounds like a rather useful read.
"A long, awkward silence" (Weird Universe)