The US government has announced plans to open more than 3m acres (about 5,000 square miles) of Alaskan wilderness to logging, mining and road building, angering environmental campaigners who say it will devastate the region. Supporters say the plan for the Tongass National Forest, a refuge for grizzly and black bears, wolves, eagles and wild salmon, will revive the state's timber industry.

The Bush administration plan for the forest, the largest in the US at nearly 17m acres, would open 3.4m acres to logging, road building and other development, including about 2.4m acres that are currently remote and without roads. About 663,000 acres are in areas considered most valuable for timber production.

The move, the latest in a long-running saga over the Tongass forest, effectively reverses the "Roadless Rule" protection given to the area by President Clinton.

Denny Bschor, Alaska regional forester who approved the Tongass plan, said it would sustain the diversity and health of the forest, provide livelihoods and subsistence for Alaska residents and ensure a source of recreation and solitude for forest visitors. "What is significant in the amended plan is our commitment to the state of Alaska to provide an economic timber sale programme which will allow the current industry to stabilise, and for an integrated timber industry to become established," he said.

Environmentalists said the plan continues a Bush policy of catering to the timber industry. Robert Vandermark, manager of the Pew environment group's heritage forests campaign, said: "In its final months, the Bush administration is attempting to give logging and mining industries the keys to the Tongass National Forest, the world's largest intact temperate rainforest. Wild areas like the Tongass contain watersheds that provide clean drinking water, wildlife habitat and outstanding outdoor recreation opportunities that should be kept safe for generations to come."

The Alaska Wilderness League said logging made up only 1% of the region's economy, much less than commercial fishing and tourism, which could be damaged by increased development.

But the Alaska Forest Association, an industry group, said the plan, which will not increase the timber take allowed from the forest, fell short of its needs. Owen Graham, the group's executive director, said: "It is critical that the final plan allows our industry to survive. Survival means returning to a realistic timber supply level in south-east Alaska, not a continuation of the starvation level we have been struggling with for the last few years." Both sides could challenge the decision, announced last Friday, in court.

The new plan stems from lawsuits filed by environmental groups in 2003 that have since shifted the Forest Service's timber sale programme away from roadless areas to land that can be reached by roads that meander for 3,700 miles through the forest. The plan does offer some protection: it puts aside 90,000 acres of old-growth reserve as off-limits to the loggers, and protects 47,000 acres of vulnerable limestone formations called karst lands. The Forest Service said it would consult with Indian tribes to protect and maintain sacred sites in the forest.