Two organizations representing major cities in the United States said they support the Clean Power Plan (CPP), which has come under fire from the Trump administration, and outlined plans to continue efforts to combat climate change, regardless of the position of the federal government.

On Tuesday, shortly after Trump signed an executive order (EO) calling for sweeping changes in the energy sector, the Mayors National Climate Action Agenda (MNCAA) issued a letter to Trump condemning the move, arguing that climate change is the “greatest single threat” to the 75 cities the organization represents.

“We write to strongly object to your actions to roll back critically important U.S. climate policies, including the CPP and vehicle fuel efficiency standards, as well as proposed budget cuts to the EPA [Environmental Protection Agency] and critical federal programs like Energy Star,” the mayors wrote, later adding “we urge you to change course, and to join us.”

The MNCAA letter had 47 signatories as of Wednesday evening, including New York Mayor Bill de Blasio, Los Angeles Mayor Eric Garcetti and Chicago Mayor Rahm Emanuel. The mayors of Atlanta, Boston, Denver, Houston, Milwaukee, New Orleans, Philadelphia, Pittsburgh, San Francisco, Seattle and Washington also signed the letter.

The mayors reaffirmed their cities’ commitments to achieving goals outlined at a climate change summit in Paris in December 2015, which the EO does not affect. They added in January, 30 cities from the organization issued a formal request for information over the potential purchase of nearly 115,000 electric-powered vehicles (EVs) for their municipal fleets.

“Climate action is also an investment in our economy and job creation — EVs, solar power, energy efficiency and battery storage are all avenues to restoring our nation’s manufacturing base and create good, middle class jobs,” the MNCAA mayors said.

In a separate statement, Garcetti, a co-founder of the MNCAA, said that “no matter what happens in Washington,” his city will continue with its plans to reduce greenhouse gas (GHG) emissions by 80% by 2050 — a goal shared by the states of California and New York.

“Nothing can stop us from investing in EVs and mass transit; from ending our reliance on coal; from installing cool roofs and pavement; or from leading America in solar power,” Garcetti said. “Los Angeles will uphold the obligation to preserve the health of our planet, protect our most vulnerable residents, and create a 21st century economy.” The mayors, he added, “will continue doing our part to meet the goals of the Paris climate agreement in cities across the country.”

On Wednesday, the United States Conference of Mayors (USCM) issued a separate statement also in support of the CPP, but did not condemn the Trump administration for its EO. Instead, it signaled support for a new rulemaking process surrounding the CPP, which experts say will take years and the end result is unclear.

“We hope as the Trump administration moves forward that the CPP will be implemented as promulgated,” said Tom Cochran, CEO of the USCM. “The rule was finalized after countless scientific, industry and governmental input. It should remain.”

Cochran added that the USCM “supports the CPP as an essential next step to address and lower GHG emissions as part of our nation’s responsibility to address global warming. The U.S. utility sector must be part of the solution and the CPP is a framework to ensure necessary reductions from this sector.”

Last June, at its annual conference in Indianapolis, the USCM issued a list of resolutions on climate change, including support for “strong federal action to achieve the U.S. commitments under the Paris agreement,” and a commitment by cities to “taking local action required to do our part to achieve the targets in the Paris agreement.”

In a related matter, more than 30 mayors at the same Indianapolis conference also signed a statement supporting local control of laws governing hydraulic fracturing (fracking). The move was seen as a symbolic gesture because fracking isn’t performed in most of the cities that the signatories represent.

De Blasio, Emanuel and Garcetti are also members of the USCM. The organization has more than 1,400 members, representing cities with populations of 30,000 or more.