President Donald Trump and California Gov. Gavin Newsom clashed again on Twitter late Tuesday, with Trump chiding the state for having the nation's highest average gas prices and Newsom slamming the president's "credibility" on environmental issues.

Three weeks after Trump announced plans to eliminate California's right to set its own auto emissions standards, he also mocked the state's move to embrace electric vehicles.

"I guess those very expensive and unsafe cars that they are mandating just aren’t doing the trick!" Trump tweeted. "Don’t worry California, relief is on the way. The State doesn’t get it!"

The average price per gallon in California was $4.18 per gallon Tuesday, according to AAA, compared to the national average of $2.64. California also charges the highest gas tax in the nation, according to the Tax Foundation, with rates of 61 cents per gallon as of July 2019.

Newsom denounced Trump's claims and sarcastically described electric vehicles as "gas guzzlers."

"You have no credibility on this issue," Newsom tweeted at Trump. "You’re trying to gut our emissions laws. Deny climate change. And wreck our environment by burning the dirtiest possible energy sources."

Environmental groups have repeatedly challenged Trump's energy policies, describing attempts to roll back methane regulations and revitalize coal as endangering the climate in the name of industry interests. Trump contended last month that loosening regulations for tailpipe discharges could save money for consumers.

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Refinery outages that have tightened the supply of gasoline on the West Coast — not emissions standards — have prompted the spike in California gas prices, AAA said.

“All regions are seeing planned and unplanned refinery maintenance, but it is only the West Coast that is really seeing gasoline stocks tighten and gas prices increase,” AAA spokesperson Jeanette Casselano said in a release. “On the whole, we are seeing gasoline demand mostly push lower amid stable, but healthy gasoline stock levels which are ultimately keeping prices cheaper for most motorists.”

The Trump administration's plan to cancel California's waiver allowing stricter emissions standards will likely face a federal court battle. Revoking the waiver also would affect 13 other states that have signed on: Connecticut, Delaware, Maine, Maryland, Massachusetts, New Jersey, New Mexico, New York, Oregon, Pennsylvania, Rhode Island, Vermont and Washington.

The back-and-forth between Trump and Newsom has been ongoing for nearly a year, with the two politicians arguing over climate, immigration, California's failed high-speed rail plans, the allocation of federal money and wildfire management.

WATCH:Trump bars California from setting fuel standards

In his first State of the State address, Newsom defied Trump’s administration by ordering hundreds of National Guard troops off the state’s border with Mexico, accusing Trump of creating a “manufactured crisis” and stressing that California would not “be part of this political theater.”

Those comments came a month after Newsom spoke out against “corruption and incompetence in the White House” during his swearing-in ceremony in Sacramento.

While campaigning ahead of last November’s midterm elections, Trump labeled Newsom as “a clown” who wants “open borders.”

Contributing: Nathan Bomey, Ledyard King, Steve Kiggins and Todd Spangler, USA TODAY.