HARRISBURG, Pa. (AP) — Pennsylvania is aiming to curb air pollution and greenhouse gas emissions from its vast natural gas exploration fields, with the governor’s administration proposing new regulations Thursday even as the Trump administration moves to relax federal requirements.

Gov. Tom Wolf’s administration brought the proposal to a technical review committee, the first step in what could be a two- to three-year process spurred by a 2016 federal requirement that applies to states and areas that don’t meet certain clean air standards.

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Wolf’s office said the governor, a Democrat, is committed to seeing the proposal through, regardless of what Republican President Donald Trump’s Environmental Protection Agency does to weaken or repeal the 2016 Obama-era rule.

Wolf’s office said the state has the legal authority to enforce its proposed rule, with or without the federal requirement.

“This process, which is just beginning, does not depend on actions by the EPA,” Wolf’s office said in a statement. The administration will, it said, work with “industry, organizations, and the public to understand any and all concerns that arise.”

Pennsylvania is the nation’s second-largest natural gas producer after Texas, and the Marcellus Shale beneath much of Pennsylvania is the nation’s most prolific natural gas reservoir.

Under the 2016 rule, qualifying states are supposed to impose new emissions controls for oil and gas field sources by early 2021.

Pennsylvania’s proposal would impose stronger limits on smog-forming pollutants — a 95 percent reduction on some sources, based on emissions reported in 2016 — and require companies to more aggressively search for methane leaks from equipment at existing oil and gas installations. Cutting smog-forming pollutants, called volatile organic compounds, has the added benefit of reducing methane emissions.

Environmental groups welcomed the proposal but say it should go further in imposing limits on methane emissions and should eliminate an exemption for equipment at low-producing well sites.

A gas-industry trade group, the Marcellus Shale Coalition, said it is concerned about the cost for companies to comply and urged the Wolf administration to wait until the Trump administration finalizes any proposed changes to the 2016 rule.

The oil and gas industry is the nation’s primary source of methane emissions, according to the EPA, accounting for nearly one-third in 2016.

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Methane is the primary component of natural gas and is one of the most potent heat-trapping pollutants, at least 25 times more powerful than carbon dioxide, the EPA says.

Earlier this year, Pennsylvania began enforcing tougher standards to reduce methane emissions and other air pollutants from new or updated equipment at well sites and on pipelines, a move environmental advocates said put the state among the leaders in going beyond federal requirements.

Colorado and California are viewed as having comprehensive regulations to reduce methane emissions. Ohio has signaled its intention to impose limits on equipment at existing oil and gas installations, and New Mexico’s incoming governor has said she plans to pursue a leak-detection rule.