WASHINGTON (AP) — The Environmental Protection Agency privately challenged the Trump administration's rationale for freezing Obama-era mileage standards, saying the proposal would actually increase U.S. highway deaths.

In announcing the mileage proposal earlier this month, officials with the EPA and Department of Transportation contended the mileage freeze would save about 1,000 lives a year. But in a June email, senior EPA staffers told the Office of Management and Budget — the White House office charged with evaluating regulatory changes — that it would slightly increase highway deaths, by 1...