Environmentally minded US states say the Trump administration’s biggest climate change rollback could increase pollution, violating federal law, according to a preview of how they will fight the federal government.

The Environmental Protection Agency is moving to replace Barack Obama’s clean power plan, a rule that would have hastened the US shift away from electricity produced from burning coal.

Not only does burning coal warm the planet, it is also causes a range of health problems, from asthma to cancer.

Where the old Obama plan would let states decide how to use cleaner sources of power, the new plan will instead encourage efficiency upgrades at coal plants.

A more efficient coal plant can run more at a lower cost and stay open longer, leading to higher levels of pollution.

The 14 states opposing the EPA rule say that it means pollution could end up higher than if the agency hadn’t written a new rule at all.

“EPA’s own analysis shows that the proposed approach has the potential to increase CO 2 and other pollutant emissions, worsen air quality, cause and exacerbate illnesses, and even contribute to deaths,” the states, which include California, New York and North Carolina, said in comments due this week.

EPA is required by law to reduce greenhouse gases from power plants. That’s why the agency is writing a replacement instead of rescinding the rule outright.

But like many of the administration’s efforts, the replacement will face vigorous opposition in the form of lawsuits once it is final. The courts could take years to make a final decision, delaying federal action on a mounting environmental crisis.

Both the states and environmental advocates said the EPA was legally obligated to explore other options to cut greenhouse gases.

“The proposal is EPA’s transparent attempt to illegally extend the lives of old, highly polluting, coal-fired power plants,” the Clean Air Task Force, an advocacy group, said in comments sent to the agency.

The states also vowed to keep working on measures of their own to combat climate change.

“While the Trump administration actively pursues opportunities to promote the fossil fuel industry over people and the environment, New York will continue to lead the fight against climate change and demonstrate a better way to protect our nation, our economy and our environment,” Andrew Cuomo, New York’s Democratic governor, said.