A spokesman for one oil company said production from shale deposits will not necessarily rely on coal plants.

Given current trends, electricity generated by natural gas, wind or solar is just as likely an energy source in 10 or 15 years, said Tracy Boyd, a spokesman for Shell Exploration and Production Co., which holds three of the six permits for the current demonstration projects.

That's the timeframe in which Shell estimates oil-shale production will become commercially viable, he said.

Colorado Gov. Bill Ritter, a Democrat, and other state officials have urged federal officials to delay a final plan and rules for commercial development. They say there are too many unanswered questions about the effects on water, wildlife, air and local economies.

They point out that companies are still experimenting with the technology and say industry and government officials acknowledge that commercial development is several years away.

President-elect Barack Obama's nominee to head the Interior Department is Sen. Ken Salazar, a Colorado Democrat who wrote the legal provision that allows the BLM to permit limited demonstration projects.