BILLINGS, Mont. (AP) — The Trump administration wants to ease restrictions on oil and gas leasing and other activities across a huge swath of the American West that were put in place to protect an imperiled bird.

The move involves conservation plans for greater sage grouse approved in 2015 under former President Barack Obama. President Donald Trump has vowed to increase U.S. energy production and open more lands to drilling.

Conservation groups critical of Trump's energy policies warned Wednesday's proposal could unravel a years-long effort to shore up the bird's struggling population.

Interior Department officials said the revisions to the Obama-era plans were aimed at increasing flexibility on public lands where the birds reside — not undoing protections outright. Colorado Gov. John Hickenlooper, a Democrat, was among elected officials in the region who voiced support for the move, saying it allowed for a "Colorado-specific approach."

Sage grouse are ground-dwelling, chicken-sized birds known for an elaborate mating ritual in which males strut around breeding grounds with large, puffed-out air sacs protruding from their chests. The species' population declined sharply in recent decades due in part to drilling, grazing and other human activities.

Wednesday's proposal affects conservation plans for grouse in Wyoming, Idaho, Nevada, Colorado, Utah, California and Oregon. The birds also are found in portions of Montana, Washington state and the Dakotas.

A spokeswoman for Interior Secretary Ryan Zinke described Wednesday's proposed changes as largely technical in nature. They were made in response to feedback the agency received about the 2015 plans from governors in sage grouse states, spokeswoman Heather Swift said.

The changes could open some areas previously closed to leasing, and allow waivers or exceptions to rules that prohibit drilling pads and wells in other areas.

"There's not a significant environmental impact," Swift said.

Kathleen Sgamma with the Western Energy Alliance said the industry lobbying group was pleased that Zinke was "moving forward with rewriting the sage grouse plans."

Environmental groups earlier this week filed two lawsuits in federal court alleging the administration since taking office has sold energy leases on hundreds of thousands of acres in at least four states in violation of the Obama-era plans.

The groups asked the courts to reverse those lease sales and block several upcoming sales.

Michael Freeman with Earthjustice, the law firm representing environmentalists in one of the cases, said the administration's latest proposal doesn't mean it can ignore the conservation plans already in place.

"They were still in effect when the lease sales were held," Freeman said.

The proposed changes are expected to be finalized in October.

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Follow Matthew Brown on Twitter at @matthewbrownap