Petrol sold in the US will contain much more corn-based ethanol under an unusual compromise among environmentalists, oil companies and farmers, Associated Press (AP) reported.

The proposal, which AP said needs congressional approval, could also be a breakthrough in the long struggle to ban an additive polluting lakes and streams.

While some details remained to be worked out, AP said, Senate negotiators have reached a general agreement on a plan that would triple ethanol use in cars and ban MTBE, a clean-air petrol additive that has fouled waterways in scores of states, according to participants in the talks.

AP said that the compromise, which would dramatically change the country's petrol, is to be part of a sweeping energy bill expected to come up before the Senate next week.

But a proposal that once was viewed as highly contentious is now likely to get broad bipartisan support, AP added.

The news agency said that the role of ethanol in petrol and the future of MTBE, the fossil-fuel base additive that has been shown to foul drinking water, has been the subject of intense political jockeying in Congress for years.

AP said that when the US government in 1995 required a minimum level of oxygen in petrol to help clean the air, most refiners turned to MTBE, although some -- largely in the Midwest -- used ethanol as an oxygenate.

Attempts by lawmakers from farming states to increase the requirements for ethanol, mostly made from corn, repeatedly failed because of opposition from oil interests and the methanol industry, AP said.

Attempts to ban MTBE, because of growing concern in some states about water pollution, have also stalled, AP added, although the Environmental Protection Agency urged phasing out the additive nearly three years ago.