"The supply of our patience may have exceeded the international demand for that patience, and we should be a little less patient and pick up the pace and work faster," Hill said.
Monday's opening meeting in the Chinese capital of envoys from the two Koreas, the US, China, Japan and Russia was the first of its kind in more than a year, and was held in the shadow of Pyongyang's first nuclear test, which it conducted on October 9.
Kim Kye-gwan, the North Korean envoy, spelled out at that session a list of demands in return for scrapping its nuclear weapons, starting with the lifting of UN sanctions and financial curbs, as well as a foreign-funded nuclear reactor for energy generation.
A separate US treasury department delegation is expected to meet the North Koreans to discuss the financial standoff on Tuesday.