WASHINGTON -- The dispute over how quickly to allow oil shale development on Western public lands flared Thursday on Capitol Hill, where a Colorado senator just introduced legislation to slow the process.

Starkly different views on whether to speed or delay federal regulations allowing development of the potential new energy source in Wyoming, Colorado and Utah emerged at a hearing of the Senate Energy and Natural Resources Committee.

Several senators, an Interior Department official and energy executives advocated for regulations to be finalized quickly in order to provide certainty for companies pursuing the energy source. But other senators, the governor of Colorado and an environmental activist said too little is known about the water and energy needs and environmental effects of development.

Congress currently has a prohibition on establishing final regulations for commercial oil shale leasing this year. But the Bureau of Land Management is moving forward with proposed regulations, which are now undergoing administrative review and should be ready for publication and public comment soon.

Sens. Orrin Hatch, R-Utah, and Wayne Allard, R-Colo., testified that the federal government needs to provide a more certain regulatory environment to foster development. But Sen. Ken Salazar, D-Colo., introduced legislation this week that would push back timelines for preparing environmental analysis and adopting leasing regulations.

Colorado Gov. Bill Ritter testified in favor of the Salazar bill. He said no one yet understands the potential impact to air and water quality, wildlife and Western slope communities nor how much water and energy would needed during the development process and from where it would come.

''Those are just some of the questions that need answering before we move ahead,'' Ritter testified.

Interior Assistant Secretary Stephen Allred said as many as 800 billion barrels of oil equivalent can be recovered, which would be a significant impact on the nation's energy supply. ''It is imperative the federal government act now to meet those future demands,'' Allred said.

He said it would be ''many, many years down the road'' before the BLM would be ready to conduct commercial lease sales. Companies now are trying the technology on a small scale of about 120 acres, and based on those results the next phase would be to scale up to areas of about 5,000 acres. The third phase would be commercial leasing.

Allred said the government would be unable to issue the second-phase research and development leases until regulations are in place. He emphasized that environmental analyses would be required at each phase.

But Salazar argued that putting the regulations in place now to allow the second phase would keep them locked in for the third phase, despite the many unknowns. ''I think we have a long way to go before we have the knowledge in hand to move forward,'' Salazar said.

Sen. John Barrasso, R-Wyo., said Congress has recognized the promise of oil shale for economic and national security. He questioned Allred about the regulatory process and spent time meeting privately with Gov. Ritter during a break in the hearing.

Jim Hansen of Oil Shale Exploration Co., which has a 160-acre research and development site in Utah, said the company's technology uses little water and once started will take no electricity. But he said if the company has to ''sit and wait'' for regulations, it will be very difficult to stay in business.

But Steve Smith of the Wilderness Society said tangible results of oil shale development are seven to 15 years away and that immense amounts of energy consumption for development would produce huge increases in greenhouse gas emissions. ''We need to go at this very carefully and very slowly,'' he said.

Terry O'Connor of Shell Exploration and Production Co. said it has five separate research and development projects and that it won't proceed with commercial development until it can clearly demonstrate to regulatory authorities that it will protect groundwater.

But O'Connor said the lack of regulations would make an already steep technological hill even harder and perhaps impossible for the company to climb. ''We're heading toward a legal train wreck,'' he said.