Bush Tries to Kickstart U.S. Oil Shale Development

That is enough to displace foreign oil imports for more than a century, said Stephen Allred, the Interior Department's assistant secretary for land and minerals management.

"Production from domestic resources makes us more secure and less vulnerable to future energy crises, and increases our security and economic well-being," Allred said. "The tremendous oil shale resources that we have in the U.S., containing several times the oil reserves of Saudi Arabia, can be a vital component of that secure future."

But Allred acknowledged commercial technology to economically tap the resource does not exist and could be a decade away from reality.

"It is going to be some time," Allred told reporters on a telephone briefing.

That is one reason the decision to issue the rules has irked environmentalists and some Democratic lawmakers, who also worry about the massive outlays of water and energy needed to convert compounds in sedimentary rocks into synthetic crude oil.