"EPA is proposing to retain without changes existing ozone requirements," agency chief Andrew Wheeler said in a telephone briefing with reporters.
The standard was set in 2015 at 70 parts per billion at ground level, down from 75 ppb set in 2008. The administration's decision came amid pressure from health and environmental groups on one side and industry lobbyists on the other.
The Obama administration said at the time that the level offered sufficient health protection.
Ozone is an odorless gas produced at ground level by a reaction of sunlight with other polluting gases emitted by power stations, oil refineries, chemical plants and cars.
It is the main component of the smog that regularly blankets cities such as Los Angeles. It is harmful to the health of people who suffer from asthma and that of children, whose lungs are still developing.
The ozone layer of the atmosphere, on the other hand, is beneficial because it filters out ultraviolet light.
The US law covering air pollution, the Clean Air Act, obliges the federal government to review its standard every five years based on health concerns and including an "adequate margin of security."
Advocacy groups, in particular the American Lung Association, were pushing for a tougher standard of 60 parts per billion.
"We're disappointed at this announcement," said the association's senior vice president of public policy, Paul Billings. "It ignores the overwhelming medical evidence that shows that a more protective standard is needed to safeguard the health of your American people."
Wheeler noted that ozone concentrations in the United States had dropped four percent between 2017 and 2019.
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