The Biden administration has reversed a Donald Trump-era drilling program by suspending oil and gas leases in Alaska's Arctic National Wildlife Refuge.
The order by US Interior Secretary Deb Haaland follows a temporary moratorium on oil and gas lease activities imposed by President Joe Biden on his first day in office.
Biden's January 20 executive order suggested a new environmental review was needed to address possible legal flaws in a drilling program approved by the Trump administration under a 2017 law enacted by Congress.
After conducting a required review, the US Department of the Interior said it "identified defects in the underlying record of decision supporting the leases, including the lack of analysis of a reasonable range of alternatives" required under the National Environmental Policy Act.
The remote, 7.9 million-hectare refuge is home to polar bears, caribou, snowy owls and other wildlife, including migrating birds from six continents.
Republicans and the oil industry have long been trying to open up the oil-rich refuge, which is considered sacred by the Indigenous Gwich'in, for drilling.
Democrats, environmental groups and some Alaska Native tribes have been trying to block it.
Environmental groups and Democrats cheered the Interior Department order, while Alaska's all-Republican congressional delegation slammed it as misguided and illegal.
The US Bureau of Land Management held a lease sale for the refuge's coastal plain on January 6, two weeks before Biden took office.
Eight days later the agency signed leases for nine tracts totalling nearly 1774 square kilometres. However, the issuance of the leases was not announced publicly until January 19, former president Donald Trump's last full day in office.