The Bush administration plans to convert more weapons-grade plutonium into commercial reactor fuel than previously planned.

A senior Energy Department official said Thursday the department has concluded that additional tons of plutonium can be taken from dismantled warheads and disposed of, beyond the 34 tons already being converted to commercial fuel.

"It will be significant," Thomas D'Agostino, head of the department's nuclear weapons program, said in an interview, when asked how much additional plutonium might be set aside for conversion.

D'Agostino said he did not want to provide a specific number of tons because the matter was still being discussed with the Pentagon.

Defense officials establish warhead needs. The Energy Department manages the nuclear weapons, including dismantling those no longer required.

The administration for years has had plans to convert 34 tons of weapons-grade plutonium into a mixed oxide fuel as part of a program with Russia where both countries agree to dispose of an equal amount of the material from their weapons stockpiles.

The U.S. plutonium is to be converted into a mixed oxide fuel that would then be burned in a commercial nuclear power reactor.

D'Agostino, meeting with a group of reporters Thursday, said the department has determined "we can add more plutonium into the mix" destined for disposal. He said decision would be unilateral and no attempt would be made to try to get Russia to match the increase.

"We want to get into a leadership position here globally and look at what minimum we need to do and what more can we do from a leadership standpoint," D'Agostino said.

The administration is preparing a report for Congress on future nuclear weapons needs and weapons stockpile size that indicates more plutonium can be converted.

The Senate Appropriations subcommittee that oversees nuclear weapons funding recently urged the Energy Department "to give greater consideration" to increase the amount of plutonium for conversion into mixed oxide fuel.

The administration hopes that the new weapons stockpile review and the decision to eliminate more plutonium might help sell skeptical lawmakers on the merits of a more robust warhead to replace the aging warheads now in the stockpile.

D'Agostino said he believes such a warhead is needed.

The administration has asked for $88 million for next budget year to examine a design and make a detailed cost estimate. The House recently refused to provide the money; a Senate committee cut it to $66 million.