WASHINGTON (AP) _ With $4-a-gallon gas grinding away at Consumers' wallets, the Bush Administration is looking to oil shale to lubricate the economy.

The government estimates the rocky deposits in the Western U.S. could eventually yield 800 billion barrels of oil. The interior department is scheduled to unveil proposed regulations Tuesday for a program to sell oil shale leases on federal lands. The rocks may be the largest untapped source of domestic oil.

Getting oil from the shale, which is concentrated in the Green River basin of Colorado, Wyoming and Utah, can be prohibitively costly and could be environmentally damaging. Unlike traditional sources of oil, oil shale requires energy to bake the rock and pump the molten oil to the surface.