The Trump administration on Tuesday advanced a plan to open nearly 45 million acres of wilderness in national forests to road construction and logging, removing protections that had been in place for a quarter century.

The proposal by the U.S. Forest Service would repeal the 2001 “roadless rule,” enacted during the Clinton administration to preserve the wild nature of forest land. It comes as President Trump pressures the agency to increase logging and to thin forests to reduce wildfire risk.

The repeal would hand a major victory to Republican-led states and industry groups that have argued for years that the prohibitions have hindered economic development. More than a dozen lawsuits have unsuccessfully sought to strike down the rule.

During his first term, Mr. Trump stripped protections from Alaska’s Tongass National Forest, the largest intact temperate rainforest in the world, only for the Biden administration to restore them in 2023.

This time, the Forest Service is eliminating protections for the nine million undeveloped acres within the Tongass, as well as millions more acres of pristine wilderness across the rest of the United States.

“For too long, outdated restrictions have kept tens of millions of forested acres off-limits to the very treatments that improve forest health and reduce wildfire risk to our communities,” Brooke Rollins, the secretary of the Agriculture Department, which includes the Forest Service, said in a statement.

Environmentalists said the plan would destroy untouched landscapes, including crucial habitats for migratory species and headwaters for major municipal water supplies. Multiple advocacy groups are expected to sue to block the repeal.

“By ripping protections from some of our oldest intact forests, the Trump administration is endangering the drinking water supplies of tens of millions and threatening wildlife habitats and recreation opportunities in almost every state,” said Drew McConville, a senior fellow at the Center for American Progress, a liberal research organization.

Roadless areas make up about 30 percent of all national forest land, encompassing nearly 60 million acres of America’s last wild areas and old-growth forests. They are home to more than half of imperiled wildlife, including grizzly bears, wolves, elk, salmon and wolverines. Forest land in the United States also absorbs millions of tons of carbon per year, helping slow climate change.

The proposal would affect the management of 44.7 million acres nationally. Idaho and Colorado have their own regulations that supersede the federal rule and insulate those states from being affected by any change in national policy.

Damien Schiff, a senior attorney with the Pacific Legal Foundation, a libertarian public interest law firm that has been fighting the roadless rule in the Tongass National Forest, said he believed the federal protections had harmed mining, timber production and other economic development. In Alaska, he argued, restrictions around the Tongass have made it difficult for surrounding communities to connect to electric grids.

“It has had a depressing impact on the use of the national forest for productive activity generally,” Mr. Schiff said.

The Trump administration and many Republicans argue that the ability to build roads would enable firefighters to more easily reach forest fires.

“For 25 years, the heavy thumb of Washington, D.C., has hindered Montana’s ability to properly manage wildfire risk and road development on nearly 60 percent of Forest Service land across the Treasure State,” Gov. Greg Gianforte, Republican of Montana, said in a statement.

Ecologists largely agree that the government needs to improve the ways it manages forest land. But experts do not agree that cutting down pristine forests to build more roads is the best way to do it.

In fact, some warned, roads could actually increase the threat of wildfires — partly because roads bring people. Nearly 85 percent of wildfires begin with human activity like discarded cigarette butts, burning debris or sparks from equipment, research has shown. Roads can also be corridors for invasive species, including flammable grasses.

“Introducing roads and human activities in areas that are otherwise undisturbed will increase wildfires where the risk is currently low,” said Alexandra D. Syphard, a senior research ecologist at the Conservation Biology Institute, a nonprofit group based in Oregon. “The unintentional impact of this could actually be creating a worse situation.”

Camille Stevens-Rumann, the director of the Colorado Forest Restoration Institute and an associate professor of fire ecology at Colorado State University, added that new roads would not necessarily help address the most destructive wildfires because they tend to ignite near existing roads. Fires in remote areas, which often are sparked by lightning strikes, tend to burn far fewer acres, she said.

“We have smoke jumpers for one, that’s how you get into those remote areas,” said Senator Martin Heinrich, Democrat of New Mexico. He noted that prescribed burns, pruning and other treatments are routine across millions of acres of forests, and those areas are afterward closed again to motorized access.

Democrats from Western states said they believed wildfire arguments were designed to hide the administration’s real goal: enabling more logging.

Mr. Trump has made timber production a top priority. Last year, he called for a 25 percent increase in logging from national forests and directed agencies to bypass endangered species protections and other environmental regulations to make it possible.

Ms. Rollins then issued a secretarial memo declaring an “emergency situation” in national forests, establishing a process for the Forest Service to fast-track logging by cutting short public participation and legal reviews.

After the proposal is published in the Federal Register, which is expected later this week, the Forest Service will accept public comments before making the rule final.