North Korea appears to be having trouble restarting a nuclear reprocessing facility that would separate plutonium for weapons from spent fuel rods, according to administration officials with access to recent intelligence.

The Bush administration had been bracing for the reclusive communist regime to time the start-up of the facility to coincide with the war with Iraq. But despite feverish activity that can be observed around the site, officials believe the North Koreans have been stymied in their rush to begin creating the raw material needed for nuclear weapons.

"They are working 24/7," a senior administration official said. "But it is not going as fast as they wanted to."

The situation has raised concerns among officials that North Korea would take other provocative steps during the conflict with Iraq. Earlier this month, North Korean fighter jets intercepted a U.S. Air Force reconnaissance plane in international airspace over the Sea of Japan, which some officials interpreted as an attempt to kidnap the crew and force the United States to begin direct talks.

Officials said the reprocessing facility, a radiochemistry lab, is built with antiquated, poorly functioning equipment that is difficult for the North Koreans to replace. The lab is adjacent to the 5-megawatt reactor at Yongbyon that the North Koreans recently restarted.

"They do not have cutting-edge technology," said another senior administration official familiar with the situation. He said steam has been seen intermittently coming out of the power plant that sits next to the six-story radiochemistry facility, which is based on a U.S. system developed in the 1950s. "They definitely are trying hard," he said.

North Korean officials have insisted the reactor, which had been shuttered as part of a 1994 agreement with the Clinton administration, is needed to produce electricity for the power-starved nation because the United States and its allies cut off fuel shipments late last year. U.S. experts, however, say the 5-megawatt plant is not large enough to provide significant electrical power and could only be intended to produce plutonium for weapons.

Robert Alvarez, a nuclear expert who as deputy assistant secretary of energy for materials asset management and national security analysis in the Clinton administration visited Yongbyon to work out details of the 1994 agreement, said the North Koreans are working with 1950s nuclear technology. He said the 5-megawatt reactor is a 1956 British design that in part still uses vacuum tubes rather than modern components. Even when operating it broke down frequently, he said.

He also said the reprocessing plant was "in the early stages of initial start-up when its activities were frozen in 1994." Trial runs would be needed before it could restart, and "it will likely require a significant amount of 'hands-on' operation that normally is done with more advanced remote controls in other countries."

Such operations in human hands generally result in spills, leaks and failures during the complex steps of extracting and purifying plutonium, Alvarez said.

While other experts have talked about the North Koreans being able to extract enough plutonium to make five or six bombs within months, Alvarez said these estimates were based on how modern, U.S. reprocessing plants operate. He said the much older, simpler North Korean facility, using older technology, could take "a span of several months to a year."

U.S. intelligence is closely monitoring the Yongbyon site from satellites and from aerial and surface scientific collectors that measure the effluent from the facilities. One clue to the return to operation of the reprocessing facility would be a brownish plume, according to one scientist.

The United States and North Korea have been in a standoff since October, when North Korean officials admitted to pursuing a covert program to produce weapons-grade enriched uranium in violation of the 1994 pact. The Bush administration demanded that North Korea dismantle its nuclear weapons programs before any negotiations could take place, and subsequently cut off shipments of fuel oil that were part of the pact. North Korea then evicted United Nations nuclear inspectors and dismantled monitoring equipment at the plant, and withdrew from the nuclear Non-Proliferation Treaty.

The administration has insisted that any discussions with North Korea over its nuclear ambitions take place within a multilateral forum that would include other key countries in the region. The administration has been unable to win much support for that approach from those nations, which have pressed the United States to begin direct talks.

One official said that the United States has "gotten vibes" that North Korea's opposition to multilateral talks may be softening. But another official said that despite proposals and ideas floated by the administration, North Korea had given no indication that any multilateral venue is acceptable.

"It would make political dialogue and finding a diplomatic way forward much more difficult if they've started the reprocessing facility," Secretary of State Colin L. Powell said earlier this week.

A plume rises from the 5-megawatt reactor at Yongbyon, North Korea, which is adjacent to the lab where efforts are underway to reprocess plutonium.