The Trump administration told an appeals court late Friday that it is considering whether it wants to repeal former President Obama’s 2015 ozone pollution rule.

Justice Department attorneys are asking the Court of Appeals for the District of Columbia to delay oral arguments scheduled for later this month in a lawsuit challenging the Obama rule, while the Environmental Protection Agency (EPA) reviews the regulation and its position on it.

“EPA intends to closely review the 2015 rule, and the prior positions taken by the agency with respect to the 2015 rule may not necessarily reflect its ultimate conclusions after that review is complete,” the attorneys wrote.

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Under the Obama administration, attorneys were defending the pollution rule against a coalition of business groups and conservative states, led by the U.S. Chamber of Commerce.

The regulation lowered the allowable concentration of ozone to 70 parts per billion, from the previous 75. Ozone is a byproduct of pollutants from burning fossil fuels and a component in smog. It is linked to respiratory ailments like asthma attacks.

The Trump administration has not stated where it stands on the rule. But it is widely opposed by Republicans, the business community and fossil fuel interests, since states would likely have to crack down on fossil fuels to meet the stricter air quality standards.

EPA administrator Scott Pruitt Edward (Scott) Scott PruittJuan Williams: Swamp creature at the White House Science protections must be enforceable Conspicuous by their absence from the Republican Convention MORE was a leading challenger of the rule before his federal position, when he was Oklahoma’s attorney general.

President Trump issued a wide-ranging executive order last week asking the EPA and other agencies to seek to roll back regulations that limit the production and use of domestic energy. The ozone rule was not mentioned specifically as a target of that order.

Repealing or changing the rule would require an extensive regulatory process that could take more than a year.

Trump attorneys have sought to stop litigation regarding numerous Obama administration regulations it opposes, including rules on hydraulic fracturing, carbon dioxide emissions from power plants and water pollution.