The announcement comes as the Obama administration and state and federal lawmakers are suddenly working to help support the flagging industry as part of the effort to reduce carbon emissions and stem global warming. Nuclear plants produce the country’s largest share of electricity without emitting carbon dioxide and can operate as needed. Their proponents are pursuing different ways to maintain the plants despite unresolved questions over waste disposal, safety and the potential for converting their operations to make weapons.

Supporters of the Exelon bailout argued that the plants were important not only to the effort to reduce greenhouse gas emissions but also to supporting thousands of jobs. But many opponents of the bailout — both some who support the use of nuclear energy and some who do not — say the public has already paid for the plants and should not have to again. And they say the company, which took in $34.5 billion in revenue last year, can afford to keep the plants open.

Executives at the company, which operates a dozen other nuclear plants in six states, ultimately disagreed and said they would continue to push for the new regulations.

The closings could put as much as $1.2 billion in annual economic activity and as many as 4,200 direct and indirect jobs at risk, including 1,500 plant workers, the company said, but employees may be able to transfer to positions elsewhere in the company.

Industry executives and supporters of the bailout bemoaned the shutdowns.

“The premature closures of Clinton and Quad Cities continue an alarming trend — our nation is losing top-performing nuclear power plants due to flawed electricity market conditions,” said Marvin S. Fertel, chief executive of the Nuclear Energy Institute, an industry trade group. “In the process, we are moving farther away from achieving our nation’s ambitious clean air commitments.”