BILLINGS, Mont. (AP) - Environmental groups, citing the dangers of global warming, want Wyoming regulators to revoke a permit for a 385-megawatt coal plant under construction.

Work on the $1.34 billion Dry Fork Station, by Basin Electric Power Cooperative, began Oct. 17 near Gillette. Gov. David Freudenthal is scheduled to attend a groundbreaking ceremony at the site today.

The groups that filed the permit appeal Thursday with the Wyoming Environmental Quality Council say Dry Fork would emit more than 3.7 million tons of carbon dioxide and other greenhouse gases annually.

The challenge to the Wyoming plant is the latest in a string of a legal maneuverings by environmental groups seeking to slow or stop new coal plant construction nationwide. Power plants are among the largest sources of greenhouse gases in the country.

"Wyoming can't just stick its head in the sand and ignore the fact that the plant will contribute significantly to global warming and also dump tons of pollution on Gillette's citizens," said Earthjustice attorney Robin Cooley, representing the Sierra Club, the Powder River Basin Resources Council and the Wyoming Outdoor Council.

The permit appeal also claims the plant would cause excessive mercury, sulfur dioxide and particulate pollution.

The Wyoming Department of Environmental Quality on Oct. 15 determined those pollution levels would fall within acceptable limits.

Basin Electric Vice President Floyd Robb said the Bismarck, N.D., utility company was reviewing the environmentalists' challenge and could not yet comment on its particulars.

"We think the Wyoming DEQ did a good job of evaluating all of the issues related to the issuance of the permit," he said.

Greenhouse gas emissions are not regulated, although an April U.S. Supreme Court decision regarding vehicle emissions said the gases should be counted as a pollutant and subject to restrictions.

In Wyoming, environmental groups have criticized the Freudenthal administration for not requiring Basin Electric to adopt technologies that would cut pollution emissions.

But a spokesman for the governor, Cara Eastwood, said much of that technology is not yet commercially viable. To wait until it was would ignore rising demands for electricity, she said.

"Just because public opinion is turning away from coal doesn't mean coal ceases to be a critically important fuel source for this country," Eastwood said.

Eastwood said Freudenthal was attending the groundbreaking because the plant would be a "significant project" entailing 1,000 temporary construction jobs and 100 permanent positions.

On Oct. 17, two days after receiving its state air permit, Basin Electric withdrew a $750 million federal loan application because it meant the plant would have faced a lengthy environmental review. Chief executive Ron Harper said potential delays in that process could have cost its members $175 million, as the cost of new plants rise in tandem with increasing material and labor costs.

The federal loan program, sponsored by the U.S. Department of Agriculture, has been challenged in a separate lawsuit filed by Earthjustice in July.

That litigation was aimed at another coal plant proposal - Highwood Generating Station in Great Falls, Mont. Attorneys involved in the suit said they hoped to use the Highwood case to scuttle the loan program altogether and slow or stop as many as six power plants.

Jill Morrison with the Power River Basin Resource Council said she believes Basin Electric withdrew its loan application because the company "saw the writing on the wall." She said the company is scrambling to beat new restrictions on carbon dioxide emissions that are being considered by Congress.

Basin Electric's Robb denied the assertion: "We are building it to meet our member demand," he said. "Basin Electric's demand has been growing 125 megawatts a year since 2005."

No hearing date on the permit appeal has been set, according to the Environmental Quality Council.