The top US negotiator with North Korea, Christopher Hill, has denied that talks on ending the country's nuclear programme have reached a stalemate.
Mr Hill said North Korea was committed to the nuclear deal
But Mr Hill made it clear the issue of whether or not Pyongyang had a uranium enrichment programme was unresolved.
He spoke a day after meeting counterpart Kim Kye-gwan for the first time since Pyongyang missed a deadline to disclose its nuclear activities.
He said Mr Kim told him North Korea was committed to the disarmament deal.
Speaking in the South Korean capital, Seoul, Mr Hill acknowledged that the talks had hit a rough patch.
North Korea failed to provide a full declaration of its nuclear activities by the end of 2007 as promised.
One issue is whether or not Pyongyang has a secret programme to enrich uranium for weapons purposes - something that the US believes but which North Korea denies.
"We cannot pretend that activities don't exist when we know that the activities have existed," Mr Hill said.
"I made it very clear that for us to proceed, we need a complete and correct declaration."
North Korea was now trying to demonstrate that equipment it had bought that could be used to enrich uranium was not being used for such a programme, he said.
The US envoy said he had also received an assurance from Mr Kim that North Korea was not engaged in proliferation.
Mr Kim "wanted to make very clear that they are not at present having any nuclear cooperation with any other country and they will not in the future have any nuclear cooperation with any other country", he said.
Mr Hill is on a tour of the East Asia region to prepare for a visit by US Secretary of State Condoleezza Rice next week.