The U.N.'s chief nuclear inspector played down expectations Monday that his trip to North Korea heralded the communist country's rapid disarmament, saying a buildup of trust and confidence were needed first.

Mohamed ElBaradei, head of the Vienna-based International Atomic Energy Agency, stopped in Beijing on his way to North Korea for discussions on how to implement a landmark nuclear disarmament agreement reached at six-nation talks last month.

"I should caution that is a very complex process," ElBaradei told reporters at the airport. "It is going to be a very incremental process. There's a lot of confidence that needs to be built."

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Under the hard-won Feb. 13 agreement, the North is to ultimately give up its nuclear arsenal in exchange for economic and political concessions.

China hosted the talks, which also involved the two Koreas, the United States, Japan and Russia.

ElBaradei is to meet with Chinese and North Korean officials during his trip, although no details have been released because the meetings have not been finalized.

He said North Korea's nuclear ambitions also were tied to security, economic and political issues, so "you have to bear with us and with the six parties as things move."

But, he said, "as long as we are talking, as long as we are making steady progress, I am quite pleased."

In 2002, Washington alleged that North Korea had a uranium enrichment program in addition to its acknowledged plutonium program. North Korea then withdrew from the Nuclear Non-Proliferaton Treaty and expelled ElBaradei's inspectors. In October, the North conducted an underground nuclear test.

ElBaradei said he hoped the talks would "provide a good framework for the agency and inspectors to return" as well as normalize North Korea's relations with the IAEA.

"We have been away for many years and it's good to go back and it's good to have a good discussion with (North Korea) and inform them that we have a job to do and we'd like to work with them," he said.

The first phase of the agreement requires North Korea to shut down its main nuclear reactor and allow U.N. inspectors back into the country within 60 days. In return, it is to receive aid equal to 50,000 tons of heavy fuel oil from the other participants in the nuclear talks.

In the next phase, North Korea is required to make a complete declaration to the IAEA and the other parties about its nuclear program, which then is to be dismantled.

"At a certain time, they need to make sure that we see everything and we are able to clarify that the program is exclusively for peaceful purposes," ElBaradei said.

U.S. Assistant Secretary of State Christopher Hill, the chief American negotiator, has said the 60-day schedule is on track so far.

Even so, work on implementing the agreement remained on shaky ground.

On Saturday, North Korea's main nuclear representative, Kim Kye Gwan, said it expects the United States to lift financial sanctions as part of the deal or North Korea will retaliate. He did not elaborate.

Washington imposed restrictions on the Macau-based Banco Delta Asia after accusing it of aiding North Korean counterfeiting and money-laundering. The restrictions are one of the main sticking points in the six-nation negotiations.

The U.S. pledged in the Feb. 13 agreement to resolve the fate of $24 million in North Korean funds frozen at the bank within 30 days. That deadline falls on Thursday.

Also last week, Wu Dawei, China's representative to the nuclear talks, cautioned that deep mistrust was undermining the process and urged countries to "improve contact and establish trust."

Complete coverage is available in FOXNews.com's North Korea Center.