The Obama administration on Sunday unveiled a tougher climate change rule for power plants, demanding that generators cut their carbon dioxide output 32 percent in the first-ever limits on the pollutant.

The historic regulation from the Environmental Protection Agency is the main pillar of President Obama’s climate agenda. It is the biggest piece of his drive to create a legacy and go down in history as the first United States president to take comprehensive action against climate change by cutting emissions of greenhouse gases such as carbon dioxide.

Obama will hold an event Monday afternoon at the White House to announce the regulation, the White House said.

The EPA is asking states to formulate plans to reach specific carbon reduction goals assigned to them by 2030, from a 2005 starting point, adding up to a 32 percent reduction nationwide. If the states do not submit plans — as multiple conservative states have threatened — the EPA will write and impose its own strategies upon them.

"In doing this, the president will take the single biggest step that any president has made to curb the carbon pollution that is fueling climate change," top Obama adviser Brian Deese told reporters Sunday.

"We already limit smog and soot pollution, as well as toxics like mercury, from our power plants. But before this rule, there were no limits on carbon," said EPA Administrator Gina McCarthy. "With this plan, carbon pollution from our power sector in 2030 will be 32 percent below 2005 levels."

The administration referred to fighting climate change as a “moral obligation” to the world’s children and called the rule “flexible and achievable.”

The administration estimates that the climate benefits, in addition to benefits from reducing other pollutants from power plants, would result in a net $46 billion benefit to the nation by 2030, along with thousands of avoided premature deaths and asthma attacks.

Compared with the carbon limits the EPA proposed last year, the final rule is 9 percent more stringent than the 30 percent cut originally envisioned.

It delays the first round of carbon goals to 2022 from 2020, a move the White House said would result in far more renewable energy such as wind and solar and less natural gas replacing coal, which is currently the dominant fuel for electricity.

But the formula for determining states’ individual carbon goals will eliminate the expectation that states implement energy efficiency measures to cut emissions. States will still be allowed to use efficiency to meet the goals, however.

And despite the added stringency, the rule is predicted to avoid little more than 0.01 degrees Celsius in global warming, since the United States’s emissions are only a small part of the world’s.

The new plan also includes incentives for states to comply early, with matching grants for reductions before the deadlines.

Nonetheless, the Obama administration sees regulations on the most carbon-intensive sector in the country as an essential step toward a strong United Nations agreement to stop climate change, which world leaders plan to sign in December in Paris.

Sunday’s announcement included two other related regulations: one with hard limits on the carbon emissions of newly-built power plants and a proposed framework for how the EPA will write implementation plans for states that do not comply.

The rules are expected to draw immediate scorn from congressional Republicans, conservative states, the fossil fuel industry and others.

Senate Majority Leader Mitch McConnell (R-Ky.) has made it a priority to fight the EPA’s main climate rule and has tried to do so with limited success through legislation, appropriations and publicly urging all of the nation’s governors to ignore it.

He sees it as an imperative to save coal, on which Kentucky’s economy is dependent.

“I can assure you, I will not stand idly by while this administration tries to wipe out the lifeblood of our state’s economy,” McConnell wrote recently in the Cincinnati Enquirer.

Multiple states’ attorneys general have pledged to file lawsuits against the rules, including those in West Virginia, Oklahoma and Texas.

Various industry groups representing different sectors have also mentioned lawsuits as a possible way to fight the regulations.

Administration officials predicted strong criticisms of what has already become Obama's most controversial environmental rule. But the critics are wrong, they said.

"Some special interest critics will tell you that it can’t be done. They’ll say we have to focus on the economy at the expense of the environment. They’ll tell you EPA’s plan will turn the lights off and send utility bills through the roof," said McCarthy.

"But they are wrong," she concluded, citing the EPA's acid rain program in the 1990s as an example of a rule that kept electricity prices stable while improving the environment and health.

"Over the next few days, we’ll hear the same tired plays from the same special interest playbook," McCarthy said. "But the American people know better."