The White House has been mulling the Willow decision for weeks. The deliberations have focused on the legal constraints posed by the fact that Conoco has held some leases for decades and “has certain valid, existing rights granted by prior Administrations, limiting the Biden Administration’s options,” the official continued.

Stopping new oil leases, plus other measures meant to conserve the Arctic from new drilling, is meant as a “fire wall” to protect 16 million acres of land and water in the state, said the official.

The Sierra Club environmental group gave tempered support to any new rules.

“These unparalleled protections for Alaskan landscapes and waters are the right decision at the right time, and we thank the Biden Administration for taking this significant step,” Sierra Club Lands Protection Program Director Athan Manuel said in a prepared statement. “However, the benefits of these protections can be undone just as quickly by approval of oil and gas projects on public lands, and right now, no proposal poses a bigger threat to lands, wildlife, communities, and our climate than ConocoPhillips’ Willow project.”