WASHINGTON - Although 2017 is the Energy Department's goal for opening the Yucca Mountain nuclear waste dump in Nevada, "the most reasonable date is probably closer to 2020, 2021," the head of the project said Wednesday.

That's because it may take a number of years for the Energy Department to get approval from the Nuclear Regulatory Commission, and there could be more litigation, said Edward F. "Ward" Sproat, director of the Energy Department's Office of Civilian Radioactive Waste Management.

Sproat also warned lawmakers at a hearing that funding for Yucca Mountain must rise above recent levels - around $500 million a year - for the program to happen at all.

"If all we can do is continue to fund the repository at that level, the repository will never be built, it will never happen," he told the energy and water development subcommittee of the House Appropriations Committee.

The program already has had to adjust to getting $100 million less in the 2007 fiscal year than President Bush requested. The final 2007 figure was $444 million.

Sproat has said that some activities are being put on hold as a result while the department focuses on its immediate goal: submitting a required license application to the Nuclear Regulatory Commission next year.

On Wednesday he warned of layoffs.

"There will be staff reductions on this program, substantial reductions, but we will get the license application completed and submitted to the NRC on time," Sproat said, without elaborating.

Sproat is asking Congress for an accounting change that would dedicate annual revenues in a special nuclear waste fund outside the overall federal budgeting process so Yucca Mountain wouldn't have to compete with other programs for funding.

That would guarantee Yucca Mountain at least $750 million per year. Once construction starts on the repository in the desert 90 miles northwest of Las Vegas, costs will soar past $1 billion per year and top out at almost $2 billion in 2012, according to Energy Department cost projections.

With Democratic Sen. Harry Reid of Nevada, an ardent Yucca Mountain foe, running the Senate as majority leader, Sproat has been working hard to impress upon other lawmakers the need to push the nuclear waste dump project forward. Yucca Mountain would be the first national repository for nuclear waste and it's meant to store at least 77,000 tons of the material, though the Energy Department is hoping it could hold much more.

There's already some 50,000 tons of radioactive waste waiting at reactor sites in dozens of states, and Sproat and others are warning that without some solution the nuclear energy industry will be in serious trouble.

Sproat also cautioned lawmakers about the growing liability to taxpayers because the Energy Department was contractually obligated to begin accepting nuclear waste from utilities starting in 1998. If the dump opens in 2017 that liability will stand at $7 billion; if the opening date slips to 2020 the liability rises to $11 billion, he said.

Sproat got a vote of support from the chairman of the spending panel, Democratic Rep. Pete Visclosky of Indiana.

"We are committed to do everything we can to ensure you have adequate funding for Yucca because I believe we do need to proceed to get it open," Visclosky said.

A Republican on the panel, Rep. John Doolittle of California, suggested that the program's fate is uncertain as long as Reid is majority leader.

"I've always supported Yucca Mountain and if there were one key retirement I think the program could move forward. I don't know what will happen in the meantime," he said.