PORTLAND, Maine — U.S. Sen. Angus King told a crowd of about 150 people Friday at a forum hosted by the Natural Resources Council of Maine that he expects a political firestorm in Congress over President Barack Obama’s new call for power plants to reduce emissions.

On Monday, the U.S. Environmental Protection Agency introduced its Clean Power Plan, calling on states to cut carbon pollution from their 2005 outputs. The rules would require Maine to cut power plant emissions 13.5 percent by 2030. The plan’s goal is to reduce carbon emissions from existing power plants nationwide by 30 percent before 2030.

King expressed satisfaction that Maine is ahead of many other states in reducing emissions but shared his concern that politics could derail that progress nationally.

“I’m very positive about the way they came about this regulation, and Maine is going to see some good changes. Already, it’s in the bank because of what has been done since 2005,” said King at the forum. “It’s gonna be a hell of a fight in the Senate though. I can’t predict the outcome.”

Others who spoke Friday credited Maine’s participation in the Regional Greenhouse Gas Initiative as a key reason for the state’s advanced position in reducing emissions from power plants.

In 2007, Maine joined the Regional Greenhouse Gas Initiative, a cooperative market-based effort among nine states to reduce climate-changing carbon pollution from power plants and spur investments in energy efficiency and clean energy. Through participation in the Regional Greenhouse Gas Initiative, Maine has been able to monitor the market related to the auction and trading of carbon dioxide allowances, and by selling its own allowances, it has generated $257 million in energy cost savings.

The Environmental Protection Agency is proposing state-specific emissions goals, but each state has broad flexibility to meet the rate by 2030, including improving energy efficiency, improving power plant operations and encouraging a reliance on low-carbon energy.

According to Bob Perciasepe, the deputy administrator of Environmental Protection Agency, Maine is well on the road to meeting its goals.

“You are not starting in Maine from ground zero,” said Perciasepe to an audience of Maine business owners and environmentalists. “You are starting on the foundation that has already been built by [the Regional Greenhouse Gas Initiative], and that is essentially taken into account with the goals set for the state.”

Perciasepe said that serious regulation of carbon emissions is well overdue, as they have been left alone for decades.

“The science is clear, the risks are clear, and costs of inaction are growing,” he said.

“Finally, as a nation, we are recognizing that climate change is real, that carbon pollution is helping to drive it, and that it’s harming our environment, our health and our future,” said Lisa Pohlmann, executive director of the Natural Resources Council of Maine.

Pohlmann said that Maine has been working to reduce its carbon emissions for years, and the new plan set forth by the Environmental Protection Agency will only “help the rest of the states catch up.”

But there are major political obstacles to overcome before that happens, King said. He foresees opposition from U.S. senators who are generally opposed to regulation, opposed to Obama — who called for the Climate Action Plan using his executive authority under the 1970 Clean Air Act — and senators from states that rely heavily on coal-powered industries.

Business interests, including the U.S. Chamber of Commerce, had prepared an attack on the proposal issued earlier this week, through a study produced by its Institute for 21st Century Energy. That report estimates the reduction plan will lower the United States’ gross domestic product by an annual average of $51 billion through 2030.

A January 2014 report on Maine’s progress toward its greenhouse emission reduction goals found that while increasing emissions correlated with growth in the state’s real GDP from 1990 to 2003, the state’s GDP did not decline as emissions dropped from 2005 to 2011.

King said he expects attempts to appeal or delay any sort of official regulation.

“I think we’ll be OK, but there’s going to be a major battle between now and November,” said King.