The American Chemical Society, an industry group, Tuesday warned Congress that without more natural gas, diesel fuel costs could soar.

Because ultra-low sulfur diesel fuel has become mandatory, more and more natural gas is being required to produce the higher-priced motor fuel. Specifically, natural gas supplies the methane, which, in turn, provides the hydrogen used by most refiners to cut sulfur levels in their diesel fuel to legally acceptable levels.

But since drilling for much of the nation`s substantial natural gas reserves is prohibited, the switch to ultra-low sulfur diesel fuel will drive up the price of available natural gas supplies.

'If the nation is to be successful in our pursuit of cleaner diesel fuel, then Congress needs to change energy policies to help bring about reliable, affordable access to natural gas,' the ACS said in a statement.

'The same goes for cleaner electricity generation, ethanol production, and solar and wind power materials -- all of which require natural gas.