The Energy Department is facing new delays in restarting crucial facilities in nuclear weapons factories, complicating decisions that must be made in the next two months about the long-term future of the bomb complex, according to agency officials and congressional and other sources.

The United States is unable to add to its nuclear arsenal because it has no facility operating to process plutonium for warheads and no functioning source of tritium, a radioactive gas used to boost the explosive power of nuclear warheads. The Energy Department weapons complex -- 17 facilities in 12 states -- has been at a near-standstill for months because of safety and environmental problems.

By Feb. 1, the Bush administration has to produce three documents revealing its thinking about future weapons production. One is the annual stockpile memorandum, in which the president lists production targets for the coming year. The second is the fiscal 1992 budget, certain to be scrutinized by Congress and environmental groups that want more emphasis on environmental cleanup than on production, especially now that the threat of nuclear war with the Soviet Union has receded.

The third is a long-term plan for reconfiguring and modernizing the complex.

This last document, due before Congress Feb. 1, is expected to recommend that most existing facilities be phased out over the next 15 years and that weapons production be concentrated at two sites -- probably Savannah River, S.C., and the Idaho National Engineering Laboratory, according to congressional sources.

Energy Secretary James D. Watkins instructed his staff last August that the long-term plan should "minimize the number of weapons production sites and the size of individual sites."

The immediate problem facing the department is how to get existing facilities back into operation while the modernization program is debated.

At Rocky Flats, Colo., the only source of plutonium triggers for nuclear warheads, the target date for the resumption of plutonium processing has receded to April at the earliest. Rocky Flats has been inactive since late last year because of safety and management problems.

The Energy Department's civilian contractor there, EG&G Inc., "put together a safety plan indicating that they could have the first building" -- a laboratory, not a production line -- "up and running by March," an Energy Department spokeswoman said. "We at DOE said we wanted more, including security upgrades, so they went back to the drawing board."

On Nov. 6, John F. Ahearne, chairman of Watkins's Advisory Committee on Nuclear Facility Safety, recommended that some of the plutonium milling work at Rocky Flats be transferred to the Los Alamos National Laboratory in New Mexico, "a significant but under-utilized asset."

But Watkins, while stressing the need to resume plutonium processing, has promised Congress that he will not attempt to transfer any plutonium operations to Los Alamos. One reason is that he wants to minimize political opposition in New Mexico to the opening of a repository for nuclear waste from the weapons complex.

More likely is an effort to begin plutonium recycling at a new Savannah River installation known as the "New Special Recovery Facility." This facility, which has been built and is undergoing environmental review, could do some of the work previously handled at Rocky Flats, but in smaller volumes, Energy Department officials said.

At Savannah River, meanwhile, the schedule for restarting the first of three reactors that produce tritium appears to have slipped again, although no announcement has been made.

The first of the three, known as K Reactor, was due to be restarted in December or January. But Watkins met last week with Savannah River officials to review new problems that are expected to lead to another postponement, according to congressional sources.

"I wouldn't be surprised if we were looking at another year," one Capitol Hill source said. "The biggest open secret in town is that the new stockpile memorandum will call for retrieving tritium from existing warheads to give DOE enough time to restart Savannah River."

Because tritium decays 5.5 percent annually, "this can't go on forever," he said, "but they may be able to stretch it out for at least a year."