The Interior Department on Wednesday made 2.6 million acres of potentially oil-rich territory in northern Alaska available for energy exploration. At the same time, it deferred for a decade any decision to open 600,000 acres of land north of Teshekpuk Lake that is the summer home of thousands of migrating caribou and millions of waterfowl.

The decision will open up for drilling much of the northeast section of the Northeast National Petroleum Reserve-Alaska, holding an estimated 3.7 billion barrels of oil, Tom Lonnie, Alaska state director for the Bureau of Land Management, said in a conference call with reporters.

The northeast and northwest portions of the reserve could yield eight billion barrels of oil, he said.

Mr. Lonnie said he expected the first oil production to begin in the easternmost part of the reserve, west of the Colville River, from 2010 to 2012. A fully developed oil complex exists on state lands on the eastern banks of the river.