In a potentially groundbreaking move, the head of the Environmental Protection Agency (EPA) has privately urged the Trump administration to reconsider a key scientific finding that has long justified U.S. efforts to combat climate change.

Four sources briefed on the matter told the Associated Press that EPA Administrator Lee Zeldin has submitted a report to the White House recommending a revision of the agency’s 2009 finding under the Clean Air Act, which determined that greenhouse gases pose a threat to public health and welfare.

The sources spoke to AP on condition of anonymity because the recommendation is not public.

This finding serves as the legal foundation for climate regulations targeting motor vehicles, power plants and other major pollution sources.