US President Joe Biden's administration has cancelled oil and gas leases in an Alaskan wildlife refuge.
The interior department said revoking the drilling leases granted under ex-President Donald Trump would preserve 13 million acres of wilderness.
But Mr Biden has not reversed his recent approval of an $8bn (£6.4bn) drilling project in the same region.
The refuge is home to grizzly and polar bears, caribou and migratory birds - and an estimated 11bn barrels of oil.
"We have a responsibility to protect this treasured region for all ages," Mr Biden, a Democrat, said in a statement on Wednesday.
The decision would protect the Arctic National Wildlife Refuge, he said, and honour "the culture, history, and enduring wisdom of Alaska Natives who have lived on these lands since time immemorial".
The decision drew praise from some local tribespeople. The Arctic Village and Venetie Tribal governments said it was "a significant step towards true, meaningful protection of these lands that are so vital to the survival of our people now and into the future".
But Republicans in the state said the move would harm Alaska Native groups who might have benefited economically from the drilling projects.
Alaska Senator Dan Sullivan said at the US Capitol in Washington DC: "[Biden administration officials] love to talk about racial equity, racial justice, environmental justice, taking care of people of colour, but one big exception - the Indigenous people of Alaska. They screw them every time."
Interior Secretary Deb Haaland argued the decision would protect a sensitive landscape that has been disproportionately affected by climate change, which is causing the Arctic to warm two-to-four times faster than the rest of the planet.
But the lease cancellations could also carry political risks with US oil prices on the rise. One industry group said it was a setback for US energy independence as Russia profits from crude sales to fund its war in Ukraine.
Kara Moriarty, head of the Alaska Oil and Gas Association, said: "What's ironic is that the Biden administration made this announcement the day after we saw more headlines about more Russian oil tankers traveling through the Bering Strait due to the war in Ukraine."
Environmental groups welcomed the interior department's decision on Wednesday, even while Mr Biden's approval in March of the Willow project - dubbed a "carbon bomb" by critics - still rankled.
The ConocoPhillips venture on Alaska's remote North Slope is expected to produce up to 180,000 barrels of oil a day and generate carbon dioxide emissions over the next 30 years equivalent to putting an additional two million cars on American roads.