The Environmental Protection Agency has placed 52 more federal facilities on its Superfund priority cleanup list, including five nuclear weapons plants ranking among the most polluted sites in the nation.

Included on the list was a Department of Energy mill tailings site in southeastern Utah.By placing the facilities on the National Priorities List of the worst toxic waste sites in the country, the EPA requires the federal agencies responsible for the pollution to sign agreements laying out cleanup goals and schedules that can be enforced in court.

"They must comply with all the standards and requirements that apply to private cleanups," said Jonathan Cannon, acting assistant EPA administrator.

The action brought the number of final or proposed sites on the priority cleanup list to 1,224; 115 are federal. EPA officials project 200 federal facilities eventually will be on the list, which includes toxic waste sites judged the greatest long-term threat to health and the environment.

While pledging to monitor vigorously compliance with new cleanup schedules, EPA officials conceded the government would be hard-pressed to come up with the billions of dollars needed.

Cannon said while many federal agencies were setting up special environmental restoration funds - such as a $500 million account recently established by the Defense Department - not all pollution problems can be addressed immediately.

"I think it's a major challenge," he said of the budget concerns. "We are going to have to work at setting priorities, at addressing the worst risks first."

Most of the 52 facilities named Thursday were military bases where years of poor waste disposal practices have resulted in contamination of local groundwater.

However, EPA officials said the most complex and extensive pollution problems were posed by the nuclear weapons plants operated for decades by the Energy Department.

The major nuclear plants listed were the Feed Materials Production Center in Fernald, Ohio, near Cincinnati; Savannah River Plant in Aiken, S.C.; Oak Ridge Reservation in Oak Ridge, Tenn.; Idaho National Engineering Laboratory in Idaho Falls, Idaho; and the Mound Plant in Miamisburg, Ohio. Officials said the Fernald site ranked among the 100 worst on the National Priorities List.

Among four other Energy Department facilities cited by the EPA was the Monticello Mill Tailings dump in southeastern Utah.