WASHINGTON (AP) — One day after 15 states sued him, Environmental Protection Agency chief Scott Pruitt backtracked on delaying Obama-era rules intended to reduce emissions of smog-causing air pollutants.

Pruitt contended his agency was being more responsive than past administrations to states' needs. He made no mention Wednesday of the legal challenges to his earlier stand.

At issue is an Oct. 1 deadline for states to begin meeting standards for ground-level ozone. Pruitt announced in June that he would hold off compliance by one year so the EPA had more time to study the plan and avoid "interfering with local decisions or impeding economic growth."

In addition to the suit by a group of states led by New York, Pruitt was sued last month by a dozen public health and environmental groups, including the American Lung Association, Physicians for Social Responsibility and the Sierra Club. The EPA was required to file a response in that case by Thursday.

Pruitt, who previously was Oklahoma's attorney general, has long opposed stricter environmental rules. At the EPA, he repeatedly has acted to block or delay regulations opposed by the chemical and fossil-fuel industries.

Wednesday's reversal was the latest legal setback for his agenda. Last month, a federal appeals court in Washington ruled that Pruitt overstepped his authority in trying to stall an Obama administration rule that oil and gas companies monitor and reduce methane leaks.

In a statement, Pruitt suggested his about-face on ozone standards simply reinforced the EPA's commitment to helping states through the complex process of meeting the new standards on time.

"Under previous administrations, EPA would often fail to meet designation deadlines, and then wait to be sued by activist groups and others, agreeing in a settlement to set schedules for designation," said Pruitt, who sued EPA more than a dozen times as a state official. "We do not believe in regulation through litigation, and we take deadlines seriously. We also take the statute and the authority it gives us seriously."

The EPA's statement said Pruitt may at some point use his "delay authority and all other authority legally available" to ensure regulations "are founded on sound policy and the best available information."

Republicans in Congress are pushing for a broader rewrite of the ozone rules. A House bill approved last month seeks to delay the 2015 rules at least eight years. The Senate has not voted yet.

New York's attorney general, Eric Schneiderman, said the states intend to keep up the pressure.

"The EPA's reversal — following our lawsuits — is an important win for the health and safety of those 6.7 million New Yorkers, and the over 115 million Americans directly impacted by smog pouring into their communities," Schneiderman said.

New York was joined in the case by California, Connecticut, Delaware, Illinois, Iowa, Maine, Massachusetts, Minnesota, New Mexico, Oregon, Pennsylvania, Rhode Island, Vermont and Washington, and the District of Columbia.

Ground-level ozone is created when common pollutants emitted by cars, power plants, oil refineries, chemical plants and other sources react in the atmosphere to sunlight. The resulting smog can cause serious breathing problems among sensitive groups of people, contributing to thousands of premature deaths each year.

"These safeguards are essential because smog pollution can trigger asthma attacks, cause irreversible lung damage or even death," said Mary Anne Hitt of the Sierra Club. "However, with an administration that prizes corporate polluters and its own extreme agenda more than the health of the public, we can't let up on our fight to protect our families."

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Follow Associated Press environmental writer Michael Biesecker at http://Twitter.com/mbieseck