The Obama administration’s controversial plan to cut power plant emissions drew around 2 million letters from supporters, detractors and energy experts before the deadline this week. The U.S. Environmental Protection Agency now has until next June to sift through comments and finalize the climate change rule.

The EPA's Clean Power Plan, a signature piece of President Barack Obama's climate change agenda, aims to reduce carbon dioxide emissions from fossil fuel plants to 30 percent below 2005 levels by 2030. To comply with the rule, each state has to create an individual strategy for reducing coal-fired electricity, increasing energy efficiency and boosting the use of solar, wind and other renewable energy sources.

Janet McCabe, the EPA’s acting assistant administrator for the office of air and radiation, said Monday that the agency received more than 1.6 million comments since unveiling the proposal in June, along with hundreds of thousands of additional comments that were submitted just before the Dec. 1 deadline. “We’ve heard from people who support EPA moving forward with the Clean Power Plan and people who don’t,” she said in a statement. “What we know for sure is that people care about this issue, and we know we have a lot to consider as we work toward a final rule.”

More than a dozen states criticized and rejected the plan in their comments to the EPA. All have large energy-production industries and are headed by Republican leaders.

Wisconsin Gov. Scott Walker said the power plant rules would impose huge regulatory costs on utilities, which would then be passed along to ratepayers and manufacturers. “I urge federal officials to carefully consider our concerns and the adverse economic impact this could have on our state, as well as the nation,” he said in a letter to the Obama administration.

In Oklahoma, the state Department of Environmental Quality said the plan was “fundamentally flawed and unworkable” and requested the agency withdraw its proposal. Oklahoma is one of 12 states, led by West Virginia, that is suing the EPA to block the emissions rule. The states argue that coal-fired plants are already regulated under a separate section of the Clean Air Act.

Supporters say the Clean Power Plan is a crucial tool for reducing emissions from power plants, which account for about one-third of America’s total greenhouse gas pollution. In comments to the EPA, a coalition of more than 200 businesses said the plan would also ramp up public and private investment in the clean energy economy, a broad sector that includes renewable energy installations, energy-saving technologies and highly efficient construction.

“As businesses concerned about the immediate and long-term implications of climate change, we strongly support the principles behind the draft carbon pollution standard for existing power plants,” according to the letter, whose signers included Fortune 500 companies such as Nestlé, Starbucks, Kellogg and Ikea.

“Our support is firmly grounded in economic reality. We know that tackling climate change is one of America’s greatest economic opportunities of the 21st century, and we applaud the EPA for taking steps to help the country seize that opportunity,” the companies wrote.

The EPA initially planned to close the public comment period this fall. But in late September, after a swell of pushback from coal-state lawmakers and industry groups, the agency extended the period by an extra 45 days. McCabe said at the time that the EPA was still working toward a June 2015 deadline, and she insisted that regulators “will have plenty of time” to finalize the Clean Power Plan before Obama leaves office.