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."

"It is irresponsible to require labels on products that are inaccurate when EPA knows the product does not pose a cancer risk," Wheeler said.

Officials at Bayer, which acquired Monsanto and its product lineup including Roundup, did not respond to a request for comment. Neither did the California Environmental Protection Agency.

A public health and environmental advocacy group said that type of announcement from the EPA is unusual.

"I can't remember EPA ever having issued a guideline saying we're not going to approve any labels that a state is requiring to warn people of a health hazard," Erik Olson of the Natural Resources Defense Council told CNN.

The EPA said did not have examples of similar announcements available on Friday.

The EPA concluded in April that there are "no risks to public health when glyphosate is used" for its currently approved uses, and that it "is not a carcinogen."

At the time of that announcement, Bayer said it "firmly believes that the science supports the safety of glyphosate-based herbicides, which are some of the most thoroughly studied products of their kind, and is pleased that the regulators tasked with assessing this extensive body of science continue to reach favorable conclusions."

Other health bodies, including the California regulators, have disagreed. The International Agency for Research on Cancer found in 2015 that it is "probably carcinogenic to humans."

Juries have also granted massive awards to people who attribute their health issues to Roundup. Those awards could add up into the billions.

Wheeler said barring the cancer warning will ensure "the information shared with the public on a federal pesticide label is correct and not misleading."