Hill said the North's envoy had been "very careful not to describe this as any kind of stalemate and he wanted to make clear that he and his government are prepared to try to make progress and get through this."
Under a six-nation aid for disarmament deal agreed in Beijing almost a year ago North Korea is required to give a full declaration of all its nuclear programmes.
The North insists it has already submitted its declaration, but the US says these do not provide a full account of all its nuclear-related activities.
Hill said North Korean officials had insisted in a meeting in Beijing earlier this week that it was not cooperating with any other countries on nuclear technology and had no plans to do so.
Another complication to the North's nuclear declaration is its alleged uranium enrichment programme.
Washington claims the North admitted in 2002 to seeking to enrich uranium, going around a freeze of its plutonium-based nuclear weapons programmes.
"We have a situation where they have purchased some equipment, and have been trying to show to us that this equipment is not being used for uranium enrichment," Hill said.
He said such evidence would be considered a positive step by the North, but that it still did not mean the issue could be dismissed.
Hill's current tour through Asia is intended to prepare the ground for a visit next week by Condoleezza Rice, the US secretary of state.
Her visit coincides with an unprecedented visit to North Korea by the New York Philharmonic to perform a concert in Pyongyang on February 26.
Hill said the orchestra's visit was a private initiative although it had the support of the US government which saw it was a demonstration that Americans bore no ill will to North Korea.