At the invitation of North Korea, nuclear experts from the U.S., China and Russia will travel to the Communist country next week to survey nuclear facilities to be shut down, the chief U.S. negotiator to six-nation nuclear talks announced Friday.

Assistant U.S. Secretary of State Christopher Hill said that the delegation of experts from the three nuclear powers would go to North Korea on Tuesday for a four-day survey "of nuclear facilities to be disabled."

"This is an idea the North Koreans came up with," Hill told reporters. He said it was hoped that the full dismantling would be completed by Dec. 31.

He said the overture by North Korea marked "another significant step toward the goal of de-nuclearization" of the Korean peninsula.

North Korea agreed in June to abandon its nuclear weapons program in exchange for fuel and other foreign aid. The deal was struck as part of longtime six-nation negotiations among North and South Korea, the United States, China, Russia and Japan.

The long-standing nuclear powers in that group — the U.S., Russia and China — were invited by Pyongyang to begin a survey of North Korean nuclear facilities that should be dismantled, Hill said.

"The experts will … engage in discussions in the scope and the technical feasibility of specific actions to be taken to disable the (North Korean) nuclear facilities," Hill said.

Hill said the visit follows the shutdown in June of the key facilities of North Korea's Yongbyon nuclear plant.  

Hill is accompanying U.S. President George W. Bush at the 21-nation Asia-Pacific Economic Co-operation forum here.

He said the invitation from North Korea came out of a U.S.-North Korean meeting that took place in Geneva.

"I think it's a sign that this current phase of disabling is an ambitious phase," Hill said. "We have a lot of work to do. It's a sign of the seriousness of purpose that all parties, including the North Koreans, bring to bear on this issue."

"Our plan is to get this done by Dec. 31. To do that we need to have some nuclear experts — get some eyes on — and we thought the sooner the better," Hill said.

Hill said there are many different ways to disable a nuclear facility so that it would be extremely difficult to bring it back online.

"You can drill a hole in the side of a reactor. You can fill it with cement," he said. "You can do various things, but it helps if you have a site survey and have a look at the reactor first."

He said it was the first time that international nuclear experts had been invited into North Korea.