The Nuclear Regulatory Commission expressed its concerns in a memo filed last week.

The agency agreed with Duke Energy Corp., which said it worries whether a Russian program to convert the plutonium into mixed-oxide fuel, or MOX, will fail before it begins.

The U.S. Department of Energy says the first trucks might roll into Savannah River Site by May 15.

Duke Energy's concerns were filed as part of the utility's plans to relicense several nuclear power plants that will use the new fuel, company spokesman Tom Shiel said.

South Carolina Gov. Jim Hodges has threatened to do anything within his power to stop plutonium shipments into the state. The U.S. Department of Energy says the first trucks might roll into SRS by May 15.

The plants to convert plutonium into nuclear plant fuel at SRS won't be complete for six years, the Nuclear Regulatory Commission said. Mr. Hodges worries that the program will never be fully funded and that the untreated weapons-grade plutonium will sit in the state indefinitely.

The MOX program is part of an international arms agreement between the United States and Russia in which each country has pledged to convert some of their plutonium, once used to arm nuclear missiles, into fuel.

If one side backs out of the agreement, the other side might not continue with it, Mr. Shiel said. Questions have surrounded the Russian program for months.

"If this doesn't occur in Russia, then it very well could not occur here," Mr. Shiel said. "In that case the problem goes away, or the Department of Energy goes in another direction."

But Department of Energy spokesman Joe Davis said the government is so committed to the MOX program that it has pledged to spend $4 billion during the next 20 years.

"This is the policy of the United States," he said.

Attorney General and Republican gubernatorial candidate Charlie Condon has called for Mr. Hodges to sign an agreement with federal officials.

Fellow GOP candidate Secretary of State Jim Miles, on the other hand, wants Democrats and Republicans to unite behind Mr. Hodges.

"We will not be the dumping ground for the rest of the country," Mr. Miles said.