Colorado has joined a growing list of states that will sue the Environmental Protection Agency to stop the implementation of President Barack Obama’s controversial Clean Power Plan.

Attorney General Cynthia Coffman said the lawsuit challenging the EPA’s authority represents “crucial litigation” against the measure first proposed last year. More than 20 states are expected to be a part of the filing.

“We have been looking at (the plan) and evaluating whether or not there is such an impact on Colorado that we needed to put our name on a lawsuit,” Coffman, a Republican, said in an interview Friday with The Denver Post. “We just determined this week that is exactly where we need to be.”

The Clean Power Plan targets existing coal-burning power plants to cut carbon emissions nationwide by 32 percent before 2030 against 2005 levels.

Obama touted the initiative as the nation’s most important step to address climate change.

In Colorado, the plan calls for a 28 percent reduction in overall carbon dioxide emissions by 2030 against 2012 levels.

Federal officials contend the plan, formally announced by Obama at the beginning of the month, can help leverage the international adoption of similar rules. Detractors have called the initiative a “war on coal” with crippling economic impacts.

“If you make a change like the one we will see if this rule is implemented, I think it has the potential to cost jobs,” Coffman said. “I think it will impact the rates that we pay for our electricity. And I think it impacts the rights of our state government to make these decisions about how electricity is delivered.”

The Colorado Mining Association, an industry association with more than 1,000 members, commends Coffman for challenging the EPA’s regulations.

“By joining this lawsuit … Coffman seeks to protect Colorado consumers from skyrocketing electricity prices as well as increased costs for all goods and services that are produced using electricity,” the association said in a news release Saturday. “The EPA regulations are legally flawed, will cost Colorado jobs and threaten the reliability of the electrical grid.”

Conservation Colorado, a nonprofit, said the lawsuit is contrary to Colorado values about clean air and water and climate change.

“The irony is that Colorado is well-positioned to meet the goals of the clean power plan because of Colorado’s leadership on expanding renewable energy, energy efficiency and promoting a cleaner energy future,” a Conservation Colorado news release said.

The lawsuit will be filed in Washington, D.C., but it is unknown when.

Support for the plan has been split along partisan lines, with a handful of Republican governors vowing not to adhere and Democrats hailing it as needed.

The attorney general’s move isn’t likely to sit well with Gov. John Hickenlooper, whose administration has been working to comply with the plan’s rules.

On Saturday, Hickenlooper’s office issued a statement that said he hadn’t seen the lawsuit and couldn’t address specifics.

“We continue to move forward with plans to ensure Colorado has the cleanest air in the nation, and our state agencies are working together toward that goal. We’ve already accomplished much with Clean Air Clean Jobs. And while we realize there is more work to do, we are confident we can reach our goal,” the statement said.

Speaking at the Rocky Mountain Energy Summit this week, the Democrat said “it’s fun to punch the EPA” after the Aug. 5 Gold King Mile spill, but he sees alignment behind the rule.

“There’s a real instinct to say, ‘Don’t you tell us what to do. We are our own bosses.’ And we are,” Hickenlooper said of the plan. “But I think we have an opportunity. We are a mile high and we have higher risks for airborne pollutants. And reducing emissions is going to help our ability and our brand.”

Coffman said her office has been in contact with Hickenlooper’s staff and that the governor’s office will continue working on its regulatory responsibilities during the lawsuit.

“It’s not our intention to interfere with them and what they believe,” Coffman said of Hickenlooper’s staff. “But the conclusion that we’ve come to is we need a legal answer from a court about the EPA’s authority.”

Bob Loevy, Colorado College political science professor emeritus, said the lawsuit shows Colorado politics are becoming “more and more” locked in on climate change as a highly politicized issue.

“I see this as just another chapter in what is becoming a knock-down, drag-out fight over environmentalism — through global warming — between the two political parties,” he said. “It makes sense that Republicans are doing what the Republicans are supposed to do and the Democrats are doing what the Democrats are supposed to do.”

He said the contention has made it “very difficult for the average citizen to know what’s going on or what the situation is.”

Coffman said the impacts of the plan in Colorado would be significant despite claims by the state’s big energy companies saying they are well on their way to meeting — and potentially exceeding — targets set in the plan.

Colorado lawmakers under a Clean Air, Clean Jobs Act in 2010 required regulated utilities to develop plans for reducing air pollution. These plans launched utilities on efforts to replace coal plants with energy generated using renewable sources and natural gas.

Coffman describes the measure as another EPA and Obama administration authority overreach. She said the decision to join the lawsuit was not made lightly. Her office waited to join the lawsuit long after other states signed on.

“It obviously took us some time to look at this 1,500-page rule and analyze it,” said Fred Yarger, Coffman’s solicitor general.

Yarger said the legal concern about the Clean Power Plan focuses on whether or not Congress intended to give the EPA authority for such regulation when it passed the Clean Air Act.

“There’s a really, really, really important legal question buried in here above all the politics, all the policy and all the science,” he said. “It benefits everybody to get the answer sooner rather than later.”

Staff writers John Frank and Elizabeth Hernandez and The Associated Press contributed to this report.