Washington (CNN) The latest clash between federal and California environmental regulators is playing out over a cancer warning on weed killer.

The US Environmental Protection Agency announced Thursday it will not approve labels including a cancer warning for products containing glyphosate, such as the popular weed killer Roundup.

California's Environmental Protection Agency includes the chemical on its Proposition 65 list that requires products to bear a label stating they're known to cause cancer. A federal court, however, has put the California labeling requirement on hold while considering a legal challenge.

It's far from the first time the Democratic-controlled state and Trump administration are at odds. The two are split over how to regulate vehicle emissions, the President's tax returns, management of wildfire risks, and the border wall, for example.

In a statement announcing the glyphosate decision, US EPA Administrator Andrew Wheeler said the agency would not "allow California's flawed program to dictate federal policy."

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