A senior U.S. nuclear scientist says North Korea appears committed to going ahead with a nuclear disarmament agreement, but wants promised energy aid first.  VOA's Stephanie Ho reports from Beijing.

Sigfried Hecker just returned from a private visit to North Korea.

Speaking to reporters in Beijing Saturday, he said North Korean officials have told him they will not provide a full declaration of the country's nuclear programs until other countries provide fuel oil and other aid.

Hecker says Pyongyang also wants to be removed from the U.S. list of state sponsors of terror.

"They said until that is done, they will not be able to produce what Ambassador Hill calls a complete and correct declaration," he said.

Ambassador Christopher Hill is the chief U.S. negotiator in the North Korean nuclear talks, which include the United States, North Korea, China, South Korea, Japan and Russia.

Under an agreement reached last year, the five other countries pledged to provide aid and other concessions to North Korea. In return, North Korea was to disable its nuclear programs and provide a complete accounting of them by the end of 2007.

Now though, the United States and North Korea differ on whether an acceptable declaration has indeed been made.  Pyongyang says it has provided all the necessary information, but Washington says the information it has received to date has not been enough.

Hecker said he was told North Korean officials have shared what they described as "very important" information with the United States about Pyongyang's highly enriched uranium program and showed U.S. officials some of the relevant material.

"So they believe they have answered the question of uranium," he added.

He says North Korean officials also are slowing down their work to dismantle the Yongbyon nuclear reactor, where Pyongyang can produce weapons-grade plutonium from approximately 8,000 spent nuclear fuel rods.

"The current rate of removal is only 30 fuel rods per day," he noted.  "That's the slowed down rate. And so you can calculate that out, that it will take many months at this rate."

In Pyongyang, North Korea's number two leader, Kim Young Nam blamed the United States for the stalemate.

U.S. and South Korean officials have said the disablement work has gone relatively well, but emphasize that it is behind schedule.

In related news, U.S. Secretary of State Condoleezza Rice will travel to Seoul later this month for the inauguration of South Korean President-elect Lee Myung-bak.  Afterwards, she will travel to China and Japan, to discuss the stalled efforts to persuade North Korea to abandon its nuclear weapons programs.