The Joe Biden administration announced Tuesday it was halting petroleum development activity on the Alaska National Wildlife Refuge, reversing a move by former President Trump to allow drilling.

This is a major blow to the long-contested quest of oil companies to drill in the sensitive territory. The push for development picked up momentum after Trump announced the leasing plan last November shortly after losing reelection to Biden.

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The US Interior Department said it was notifying firms of the freeze, pending a comprehensive environmental review that will determine whether leases should “reaffirmed, voided or subject to additional mitigation measures,” the agency said in a statement.

At a lease sale in January, US officials auctioned off 11 oil tracts. Major oil companies sat out the bidding, and nine of the leases went to the Alaska Industrial Development and Export Authority, a state agency, while two went to small companies.

Biden had promised to protect ANWR during the presidential campaign.

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White House climate advisor Gina McCarthy noted Biden’s promise and said the move reflected his belief that “national treasures are cultural and economic cornerstones of our country,” according to a White House statement. 

Biden “is grateful for the prompt action by the Department of the Interior to suspend all leasing pending a review of decisions made in the last administration’s final days that could have changed the character of this special place forever,” McCarthy added.