Interior Secretary Ken Salazar speaks during a news conference Monday in Anchorage. (Mark Thiessen/AP)

Interior Secretary Ken Salazar on Monday announced the first comprehensive plan to manage the National Petroleum Reserve in Alaska, allowing for new drilling on half of the nearly 23 million-acre reserve while putting the rest off-limits to oil and gas exploration.

The move — which leaves open the possibility of constructing a pipeline to transport oil and gas extracted from the Chukchi Sea onshore — drew praise from environmentalists but sharp criticism from oil and gas proponents who said it would restrict the industry’s ability to tap the nation’s hydrocarbon resources.

“This will provide a road map to help facilitate the transition from leasing and cautious exploration to production and smart development,” Salazar said at a news conference in Anchorage, adding that he worked to balance protecting “an iconic place on our Earth” with the need for “a plan that will allow the industry to bring energy safely to market from a remote area.”

Companies have conducted exploratory activities on the North Slope reserve during the 1980s and in recent years. Nearly 3 million acres of the reserve is under lease, but production has not begun; under the proposal, 11.8 million acres will be opened for development.

Many subsistence hunters and environmentalists lobbied to protect habitat for two of the nation’s largest caribou herds, as well as endangered spectacled eider ducks and other Arctic species; the plan released Monday was the most protective of four alternatives the Interior Department had put out for public comment.

In a statement, Cindy Shogan, executive director of the Alaska Wilderness League, hailed Salazar for striking “a needed balance between responsible development, and conservation of special areas within the reserve. . . . Protecting the caribou herds’ migration corridors, calving grounds, insect relief area and wintering grounds will protect and preserve the Alaska Natives’ subsistence way of life for now and into the future.”

Erik Milito, the American Petroleum Institute’s group director of upstream and industry operations, said the plan “continues to leave domestic energy resources, jobs and government revenue off the table.”

And while Salazar said the plan would not block an oil and gas pipeline traversing the reserve, Sen. Mark Begich (D-Alaska) issued a statement saying he was “very concerned” that the plan “still seems to close off several options for building a pipeline across the NPR-A.”

Meanwhile, ongoing regulatory delays have raised questions about what sort of offshore oil drilling Royal Dutch Shell will be able to conduct in the Chukchi this summer. Shell spokeswoman Kelly op de Weegh said progress on constructing and certifying the firm’s Arctic Challenger containment barge “remains steady.”

“There’s no set timeline for the completion of this important process,” she said in an e-mail. “Our goals remain to drill this season and complete as many wells as possible.”

Salazar told reporters that while “we don’t have a lot of time,” federal officials will not sign off on Shell’s operations until they have met the government’s strict safeguards.

“This is the most cautious, highest-guarded activity in the history of any kind of ocean energy development,” he said. “I will hold their feet to the fire and do everything I can to make sure they abide by the standards and regulations we have set.”

The National Petroleum Reserve, which is the size of Indiana, was established by President Warren G. Harding in 1923 to ensure that the U.S. Navy had sufficient energy supplies as it moved from coal-burning to oil-burning ships.