(Bloomberg) -- California’s top clean-air official fired back against Trump administration charges that the state hasn’t done enough to fight pollution within its borders, saying the U.S. Environmental Protection Agency should “do its job.”

Last month, EPA Administrator Andrew Wheeler warned California Air Resources Board Chairman Mary Nichols that federal highway funds for the state might be withheld over a backlog of incomplete state plans to fight air pollution.

Nichols responded in a letter on Wednesday, saying most of those plans await EPA action to be implemented and cited EPA staff shortages, competing priorities and unclear guidelines from Washington as the result of the “multi-year delays” in finalizing the plans.

“None of your agency’s administrative delays have had any impact whatsoever on public health because California has moved ahead with implementation in the absence of U.S. EPA action,” Nichols wrote. “Under these circumstances, your sanctions threat is at best unfounded.”

Wheeler had asked Nichols to say by Oct. 10 whether the state planned to withdraw the more than 130 backlogged plans to curb pollution. Nichols said the state would withdraw those for which “EPA action is no longer needed.”

The back-and-forth is part of an wide-ranging feud between the Trump administration and California officials that has recently escalated over environmental policy. The EPA last month moved to revoke California’s power to curb greenhouse gas emissions from autos, and slammed the state for pollution linked to the state’s homeless population.

California has long been known as a liberal bastion, politically and culturally, and President Donald Trump often assails policies of the state and its cities, and even did so on his way back to Washington from a visit last month.

Wheeler’s letter chided California for its air quality, calling it the nation’s worst and saying the state “has failed to carry out its most basic tasks under the Clean Air Act.”

Nichols took exception, calling his charge “simply false.”

“Rather than mischaracterizing U.S. EPA’s backlog as the result of California’s purported failure to implement the Clean Air Act and threatening to withhold California’s transportation funds,” Nichols said, “it is imperative that U.S. EPA move quickly to do its job and reduce pollution from the sources it has the responsibility to regulate.”

--With assistance from Jennifer A. Dlouhy.

To contact the reporter on this story: Ryan Beene in Washington at rbeene@bloomberg.net

To contact the editors responsible for this story: Jon Morgan at jmorgan97@bloomberg.net, John Harney

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