UN nuclear watchdog head Mohamed ElBaradei has said that North Korea is still "fully committed" to giving up its nuclear programme.
Mr ElBaradei is back in Beijing ahead of six-party talks on Monday
He was speaking in Beijing after holding talks in North Korea, which he described as "quite useful".
He was hoping to arrange for the return of UN nuclear inspectors, seen as key to the success of a recent deal.
Last month, North Korea agreed to end its nuclear programme in return for large quantities of foreign aid.
This was Mr ElBaradei's first visit to North Korea, and the IAEA's first since Pyongyang threw out its nuclear inspectors in 2002.
"The DPRK [North Korea] said they were committed to the denuclearization of the Korean peninsula," he said on his return to Beijing.
"It is in the interests of North Korea to normalise relations with the IAEA [International Atomic Energy Agency]," he told a news conference. "We cleared the air. We opened the door for a normal relationship."
N KOREA NUCLEAR DEAL
N Korea to 'shut down and seal' Yongbyon reactor, then disable all nuclear facilities
In return, will be given 1m tonnes of heavy fuel oil
N Korea to invite IAEA back to monitor deal
Under earlier 2005 deal, N Korea agreed to end nuclear programme and return to non-proliferation treaty
N Korea's demand for light water reactor to be discussed at "appropriate time"
But officials in Pyongyang had made clear that US financial sanctions had to be lifted first before talks could move forward, he said.
Mr ElBaradei said this was a long process - "the proof of the pudding is in the tasting, and we have not yet tasted the pudding," he added.
Mr ElBaradei was reportedly unable to meet the North's top nuclear negotiator Kim Kye-gwan as planned on Wednesday, because of scheduling problems.
Mr ElBaradei met instead with another minister, because Mr Kim was busy preparing for forthcoming six-party negotiations, according to an IAEA spokeswoman.
Six-nation working group discussions resume on Monday in Beijing involving officials from the US, China, Russia, Japan and the two Koreas.
The deal called on the North to "shut down and seal" its Yongbyon facility within 60 days in return for fuel aid.
South Korea earlier said it had seen no sign that the North was shutting down its main nuclear facility, a key part of the landmark deal reached last month.