The federal agency charged with protecting endangered species like the brown pelican and the Kemp’s ridley sea turtle signed off on the Minerals Management Service’s conclusion that deepwater drilling for oil in the Gulf of Mexico posed no significant risk to wildlife, despite evidence that a spill of even moderate size could be disastrous, according to federal documents.

By law, the minerals service, before selling oil leases in the gulf, must submit an evaluation of the potential biological impact on threatened species to the Fish and Wildlife Service, whose responsibilities include protecting endangered species on land. Although the wildlife agency cannot block lease sales, it can ask for changes in the assessment if it believes it is inadequate, or it can insist on conducting its own survey of potential threats, something the agency has frequently done in the past.

But in a letter dated Sept. 14, 2007, and obtained by The New York Times, the wildlife agency agreed with the minerals service’s characterization that the chances that deepwater drilling would result in a spill that would pollute critical habitat was “low.”

The agency signed off on the minerals service’s biological evaluation, even though that assessment considered only the risks to wildlife based on spills of 1,000 to 15,000 barrels  a minuscule amount compared with the hundreds of thousands of barrels now spewing into the gulf. The assessment also noted that even such modest spills carried up to a 27 percent risk of oil reaching the critical habitat for some endangered species.