The latest congressional salvo against the U.S. Environmental Protection Agency will come in a Senate vote Thursday to block a regulation on coal-fired power plants that is vigorously opposed by the Southern Co. and other utilities.

Even though the vote is likely to fail because even Republicans are not universally in favor of the proposal by Sen. Rand Paul, R-Ky., it will pave the way for other proposals with support in both parties to delay the rule’s implementation, now scheduled for January.

Paul's proposal would overturn the EPA’s cross-state pollution rule, which requires power plants to cap and regulate two major pollutants. The rule is a rewrite of a Bush administration rule that was overturned in the courts in 2008.

The White House threatened to veto the measure, saying in a memo that it “would cause substantial harm to public health and undermine our Nation's longstanding commitment to clean up pollution from power plants.”

Atlanta-based Southern, though, says the cross-state rule and pending mercury regulation would require Georgia Power and other Southern utilities to spend billions to close coal and oil plants or retrofit them with pollution control equipment, which takes years to design and build. Customers pay for those costs in the form of higher electric bills, pending approval from state utility regulators.

A veto probably will not be necessary as Sen. Lamar Alexander, R-Tenn., broke ranks with most of his party to oppose Paul -- but Alexander has a plan with Arkansas Democrat Mark Pryor to move the compliance deadline to January 2013. Other senators also have legislation to postpone the rule, including Nebraska Republican Mike Johanns, who is seeking a two-year delay.

The EPA has considered a suite of environmental rules aimed at power plants and other heavy industry. Of these, the cross-state rule, which requires power plants to cap and regulate certain emissions, and mercury regulations could have the most impact on Southern and its operating utilities. These are the rules that target coal-fired power plants, and Southern still gets about half its power from the heavy-polluting fossil fuel. Southern has publicly fought against the rules and spent $6.15 million on lobbying in Washington during the first half of this year, according to the Center for Responsive Politics.

The EPA must issue a final mercury rule by Dec. 16. A bill has already been introduced by Sens. Joe Manchin, D-W.Va., and Dan Coats, R-Ind., that would give utilities until Jan. 1, 2017, instead of 2015, to meet the mercury standards. Some say that's still not enough time for utilities to do the necessary work.

Georgia GOP Sens. Saxby Chambliss and Johnny Isakson plan to vote for Paul’s proposal, and Isakson has also expressed support for the various pitches to delay the rule.

But environmental groups are lining up against any sort of proposal to scrap the cross-state rule, which would save Georgia at least $3.3 billion a year in health care costs from asthma and other respiratory diseases, said Colleen Kiernan, director of the Sierra Club's Georgia Chapter.

"If Senators Isakson and Chambliss care about Georgia's economy, they will vote against any dismantling or delay of the cross-state air pollution rule," she said.

Georgia and 26 other states have sued the EPA to try to block the cross-state rule and joined 24 other states in efforts to delay issuance of the mercury regulations. For its part, Southern has petitioned the EPA to reconsider and filed suit in the U.S. Court of Appeals for the District of Columbia Circuit. Stephanie Kirijan, a company spokeswoman, said part of Southern's opposition is "due to the unreasonable compliance time lines."

Southern hasn’t tallied exactly how much it will cost to meet the cross-state and mercury standards, Kirijan said, but pollution controls are pricey. Georgia Power has said installing equipment known as scrubbers can cost between $300 million and $1 billion each. Putting baghouses, which curb mercury pollution on four units at Plant Scherer, totaled $558 million, the company said.

“The rules as proposed would be economically devastating with little economic benefit. It’s just cost, cost, cost,” said Scott Segal, director of the Electric Reliability Coordinating Council, a coalition of energy companies that includes Southern.

But Kiernan, from the Sierra Club, said that without the cross-state rule, Georgia would be at an economic disadvantage.

"Our upwind neighbors contribute significantly to our air pollution problems," she said, "and in order for new industry to come to Georgia, pollution blowing in from other states must be reduced."