"There's a way forward for Kim Jong-Il, and an important step is a full declaration of programs, materials that may have been developed to create weapons, as well as the proliferation activities of the regime," said Bush.

The US president did not specify a timetable, and top US officials have suggested that a December 31 deadline for a full declaration may slip into early 2008.

Bush did not comment on North Korea's response to his first direct communication with Kim, a December 1 letter. The White House confirmed an earlier announcement that North Korea had provided a "verbal reply" via diplomats in New York.

When asked to confirm that the reply was actually from Kim Jong-Il, Scott Stanzel, a White House spokesman, said: "It was from him."

Bush added: "I got his attention with a letter, and he can get my attention by fully disclosing his programs, including any plutonium he may have processed and converted -- whatever he's used it for, we just need to know."

"As well, he can get our attention by fully disclosing his proliferation activities," said Bush, who underlined the importance of six-party efforts to dismantle the Stalinist regime's nuclear weapons programs.

That diplomatic effort groups China, Japan, Russia, North and South Korea, and the United States.

"All members of the Six Party Talks look forward to the full implementation of the September 19, 2005 Joint Statement and the denuclearization of the Korean peninsula," US National Security Council spokesman Gordon Johndroe said earlier, declining to discuss the content of the reply.

But a US official who asked not to be named summed it up as: "We'll live up to our side. We hope you live up to yours."

In his letter, the US president urged Kim to fully disclose his secretive country's atomic activities as agreed by year's end and held out the prospect of normalized diplomatic relations.

"I want to emphasize that the declaration must be complete and accurate if we are to continue our progress," Bush wrote, according to a US official familiar with the content of the letter.

US State Department spokesman Sean McCormack told reporters it was premature to assess whether the North Koreans would meet their obligations.

"The assessment point is at the end of the year or close to the end of the year when you have a disablement phase completed, when you have what the North Koreans say is their full and complete declaration," McCormack said.

But there is movement, he added.

"You can say the disablement process is going forward, you could say that the North Koreans are working on a declaration, but we're not yet at a point at at which we give an assessment 'here's where this process stands,'" he said.

McCormack said there was no sign of anything amiss.

"We haven't heard anything from North Korea that would indicate they're backing away from their commitment to fulfill their obligations," McCormack said.

The North shocked the world with its first nuclear test in October 2006.

It agreed in February in the six-party talks to disable its plutonium-producing plants and declare all nuclear programs and facilities by year-end in return for major energy aid.

In reply to a question about North Korea's past abductions of Japanese nationals, McCormack said: "We want to see the abduction issue resolved.

"We have identified it as a critical issue in the context of the six-party talks, a critical issue for a close friend and ally," Japan, McCormack said.

"And we have encouraged North Korea and Japan to work through their channels in the six-party talks to resolve the issue," he added.