That comes after The Washington Post reported on the tab for Pruitt's earlier travels, including a trip to Italy last June that cost the agency at least $120,000 for the administrator, his aides and his personal security detail. That could, in turn, create the prospect that automakers would produce different cars for sale in different areas - a practice they are loath to do.
However, green groups will harbour hopes they could protect the planned standards through potential legal action.
The U.S. fleet averaged 31.8 mpg for model year 2017, according to federal figures.
Mary Barra, the head of General Motors, said last month her company is committed to zero emissions and an all-electric line. "They do not deserve to be saddled with gas-guzzling vehicles that will wreak havoc on their household finances when gas prices inevitably spike again". "So, to ensure ongoing fuel economy improvement, the wisest course of action is to keep new vehicles affordable so more consumers can replace an older auto with a new vehicle that uses much less fuel - and offers more safety features", said Gloria Bergquist, vice president, communications and public affairs for the Alliance of Automobile Manufacturers.
The environmental regulator claimed regulations set by the former President were not practical or affordable for auto manufacturers, would cost consumers more and could even risk safety. This evaluation would determine whether the standards remain appropriate or should be made more, or less stringent.
But there is no guarantee such an effort will succeed.
The long-anticipated move is a win for auto manufacturers, which had lobbied for lower fuel-economy standards.
While clean-energy and energy-efficiency advocates, led by the state of California, staunchly oppose the EPA's latest move, the auto industry isn't exactly pushing back.More news: United Kingdom scientists unable to identify Russian Federation as source for nerve agent
But the Trump administration and California are at odds on a number of issues, and it's unclear if either side would be willing to make a concession. "Anything that falls short of a National Program with an aligned set of standards will fail to provide the long-term planning certainty suppliers need".
The original standards were seen by proponents as a way to spur innovation in clean vehicle technologies.
It said the timeline for shifting to cleaner vehicles laid out under the Obama administration is inappropriate and sets standards too high. "Keep fighting. We've got your back", Trump told Pruitt, the official told Reuters.
Pruitt added his team will examine the waiver that lets California regulators set their own pollution standards. "It is in America's best interest to have a national standard, and we look forward to partnering with all states, including California, as we work to finalize that standard", said Administrator Pruitt. In the meantime, automakers have to proceed with plans for new cars and trucks under the current gas mileage requirements because it takes years to develop vehicles.
However, sales of hybrid and electric cars have not become a significant source of sales, and consumer tastes have shifted away from cars toward trucks, sport utility vehicles (SUVs), and crossovers.
"This illegal rollback of achievable, commonsense fuel efficiency and pollution standards for cars will result in higher fuel costs and more unsafe air pollution, including the carbon dioxide that drives climate change - creating real, direct and damaging impacts on New Yorkers and our environment".
"These roll-backs from Scott Pruitt mean Americans will pay more at the pump while our air gets dirtier, just so Pruitt can help the corporate lobbyists and polluters who give him favors and marching orders", stated Michael Brune, Sierra Club Executive Director.
Pruitt has declined to comment on the rental arrangement reported last week and a spokesman for the agency on Friday defended his conduct and said the lease agreement was in line with federal ethical regulations.