In an Oct. 19 letter, 19 former U.S. Forest Service leaders asked Secretary of the Interior Sally Jewell and Secretary of Agriculture Tom Vilsack to cancel all oil and gas leases in the Badger-Two Medicine area east of Glacier National Park.

Earlier this month, a federal judge criticized the U.S. government for its delays on a more than 30-year-old drilling proposal in the area, which is considered sacred to the Blackfeet Tribe and related tribes in Canada. Of dozens of leases in the 165,588-acre Badger-Two Medicine area granted to drilling companies in the 1980s, only 18 remain.

The Louisiana-based Solenex LLC is one of the remaining lease holders and is suing the federal government for delaying a decision to allow drilling or cancel the lease. U.S. District Judge Richard Leon ordered the government to accelerate its review of the lease during an Oct. 6 hearing.

The letter commends a recent conclusion by the Advisory Council on Historic Preservation that determined the proposed oil and gas drilling fails to mitigate potential damage to cultural and historic values to the tribes.

“Our careers have been marked by compromise, collaboration and finding appropriate mitigation measures for potential impacts of a full spectrum of development,” the letter reads. “We see no feasible mitigation that will allow drilling in the Badger-Two Medicine to go forward without serious and permanent impacts on the traditional use, protection and sacredness of this land and the Blackfeet Nation,” the letter reads.

Included among the signers are former Forest Service Chief Dale Bosworth and former forest supervisors for the Lewis and Clark, Lolo, Nez Perce, Custer and Clearwater National Forests.

The Associated Press contributed to this story.