The Biden administration appears poised to approve a major oil drilling operation on Alaska's North Slope, where an untapped federal petroleum reserve is being explored as a potential future energy source for the United States.

The proposed Willow Development Project -- which is situated on land leased for decades by ConocoPhillips -- required the government to first conduct an environmental impact study, the results of which were released Wednesday by the U.S. Bureau of Land Management.

Despite "substantial concerns," the government indicated tentative approval for the project to move forward, but stipulated stiff conditions that include newly established protections for wildlife in the region and paring down the overall size of the project from five wellheads to three.

The move was likely to trigger legal challenges from environmentalists and native populations in the region.

The Interior Department, which emphasized that no final decision had been made, said it would propose a "preferred alternative," as required under the National Environmental Policy Act, but that this "does not constitute a commitment" to the project being approved.

"That decision may select a different alternative, including no action, or the deferral of additional drill pads beyond the single deferral described under the preferred alternative," the Interior Department said in a statement.

The government said it plans to make its final decision on the Willow project by next month, but environmental groups were already seething over an apparent about-face by President Joe Biden, who has continually vowed to protect the environment, reduce carbon emissions, and promote clean energy since he became president more than 24 months ago.

The administration has made several previous attempts to curtail or eliminate oil and gas development on federal territory, but the sheer scope of this proposal -- which could potentially sully the biggest swath of pristine public land in the country -- has significantly raised the stakes.

The supplemental environmental impact statement released Wednesday by the Bureau of Land Management estimates the Willow project would create about 9.2 million metric tons of carbon dioxide per year, and threaten multiple freshwater sources, and thousands of migratory animals with miles of pipelines and gravel and ice roads.

Asked about the project during a Wednesday news briefing at the White House, press secretary Karine Jean-Pierre said the president remained committed to the environment but emphasized that Biden faced an insurmountable challenge.

"The president has done more than any other president on this front," she said, rejecting the emerging criticism from environmental advocates. "He continues to deliver on historic climate change action while carrying out the law and meeting our energy needs."

While the government owns the National Petroleum Reserve in Alaska, the land has been leased since 1999 by ConocoPhillips, which plans to spend up to $10 billion to get the Willow operation up and running -- a price tag larger than any other current oil project in the nation.

ConocoPhillips, which runs two other wells in the same region, initially wanted to break ground on more than 616 acres, but the government demanded the project be kept to about 550 acres in an effort to protect native species. Company executives have previously indicated that the smaller acreage was the bare-minimum required for the plan to be workable.

In a separate statement, the company said it would meet the government's demands once a final decision was made.

"The three core drill sites ... provide a viable path forward for development of our leasehold," the company said in a release.

The reserve is believed to hold one of the biggest mother lodes of crude in North America, with new drilling standing to produce as much as 614 million barrels of oil over the next three decades.

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