By Valerie Volcovici

WASHINGTON (Reuters) - The U.S. Forest Service, which manages millions of acres of national forests and grasslands, on Wednesday proposed "bold" changes for how it carries out environmental reviews of logging, road building and mining projects on public land, a move that raised red flags for environmental groups.

The U.S. Department of Agriculture's Forest Service published proposed changes for how it complies with the National Environmental Policy Act (NEPA), a decades-old law that requires detailed analysis to be conducted before approving projects that could significantly affect the environment.

The agency's proposals include vastly expanding the categories of project types that would be excluded from lengthy environmental assessments or impact studies, which it says would "save time and resources" and make it easier to repair infrastructure like roads, trails and campgrounds and protect the public from wildfires.

"With millions of acres in need of treatment, years of costly analysis and delays are not an acceptable solution," said USDA Secretary Sunny Perdue.

It is the latest move by the Trump administration to streamline infrastructure projects on federal land and follows the lead of the Interior Department, which last year proposed major changes in how it follows the NEPA process, including cutting environmental reviews down to two years.

The administration is also expected later this month to complete the first major overhaul of NEPA in decades.

Environmental groups have warned that efforts to streamline the NEPA process curtail public input.

"This is in line with the Trump administration's approach to cutting the public out of the process to protect public land," said Randi Spivak of the Center for Biological Diversity.

The Forest Service is proposing to create a new list of "categorical exclusions," a classification under NEPA that excludes certain routine activities, such as restoration projects, roads and trails management, from time-consuming environmental assessments or environmental impact statements.

It would also enable major projects that would normally require a detailed environmental impact study to skip such a review if its proponents can find a previous analysis of a similar type of project.

Susan Brown, a lawyer with the Western Environment Law Center, said the exclusions would enable miles of road construction, open thousands of acres of land at a time to logging and allow mining exploration without an extensive review.

"These are not minor tweaks. This is major," said Brown. "This proposed rule would hide a lot from the public."

Brown said that cutting the public out of the NEPA process does not speed up projects but forces environmental groups to take legal action.

"The only thing this is going to result in is more lawsuits," she said.

(Reporting by Valerie Volcovici; Editing by Dan Grebler)