WASHINGTON (AP): The Energy Department will tell Congress in the coming weeks it should begin looking for a second permanent site to bury nuclear waste or approve a large expansion of the proposed waste repository under a mountain in the Nevada desert.

Edward Sproat, head of the department's civilian nuclear waste programme, said Thursday the 77,000-ton limit Congress put on the capacity of the proposed Yucca waste dump will fall far short of what will be needed and has to be expanded. If not, another dump must be built elsewhere in the country, Sproat said.

The future of the project beneath Nevada's Yucca Mountain is anything but certain.

President-elect Barack Obama has said he does not believe the site 90 miles (145 kilometers) northwest of Las Vegas is suitable for keeping highly radioactive used reactor fuel up to a million years and believes other options should be explored.

Sen. Harry Reid, leader of the Senate's Democratic majority and a resident of Nevada, has vowed to block the project.

Sproat, addressing a conference on nuclear waste, said the Energy Department will send a report to Congress in coming weeks that will maintain the Yucca site will need to be expanded. He said within two years the amount of waste produced by the country's 104 nuclear power plants plus defence waste will exceed 77,000 tons. Yucca Mountain is not projected to be opened before 2020 at the earliest.