SYDNEY – North Korea has invited nuclear experts from America, China, and Russia into the country to survey and recommend ways of disabling all of its atomic facilities by the end of the year, the chief American envoy to the communist regime announced today.

Assistant Secretary of State Christopher Hill called the overture “another significant step toward the de-nuclearization” of the Korean peninsula. He said the team of experts would go to North Korea on Tuesday for an initial four-day survey.

“This is the first time we’ve had real nuclear experts” from the three nuclear states in the six-party talks “go and have a look,” Mr. Hill said.

He said they would work with North Korean officials to discuss sites they would be surveying.

“I think it’s a sign that this current phase of disabling is an ambitious phase,” Mr. 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.”

Mr. Hill is accompanying President Bush, who is here attending the 21-nation Asia-Pacific Economic Cooperation forum. Mr. Hill made the announcement during a White House briefing on Mr. Bush’s activities, which included a tense meeting earlier today with President Roh of South Korea.

Under a deal reached in February after years of tortuous negotiations, North Korea agreed to relinquish its nuclear programs, including one that has produced bomb material. In return, Washington agreed to open talks on establishing normal diplomatic relations with the North and to explore removing a terrorism designation for Pyongyang, among other inducements.

The parties to the agreement include China, Japan, Russia, and South Korea as well as America and North Korea.

“This is an idea the North Koreans came up with,” Mr. Hill said of the plan to let outside nuclear experts in.

He said it was hoped that the full dismantling would be completed by December 31.

“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,” Mr. Hill said. The visit follows the shutdown in June of the key facilities of North Korea’s main Yongbyon nuclear reactor.

Mr. Hill said the invitation from North Korea came out of an American-North Korean meeting that took place in Geneva last weekend.

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

“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.”

Asked whether the December 31 goal for disabling all of the reclusive regime’s nuclear sites could be met, Mr. Hill said: “Our plan is to get this done by December 31st. To do that, we need to have some nuclear experts get some eyes on, and we thought the sooner the better.”