WASHINGTON — The Obama administration is setting aside 187,000 square miles in Alaska as a "critical habitat" for polar bears, an action that could add restrictions to future offshore drilling for oil and gas.

The total, which includes large areas of sea ice off the Alaska coast, is about 13,000 square miles, or 8.3 million acres, less than in a preliminary plan released last year.

Tom Strickland, assistant secretary for fish, wildlife and parks at the Interior Department, said the designation would help polar bears stave off extinction, recognizing that the greatest threat is the melting of Arctic sea ice caused by climate change.

Fuel tank cracks delay space shuttle launch

CAPE CANAVERAL, Fla. —Baffled by fuel tank cracks, NASA announced another launch delay for space shuttle Discovery on Wednesday and raised the prospect of a Christmastime flight.

Shuttle managers refused to set a new launch date for Discovery's final flight, on hold since the beginning of November.

The next launch opportunity would be Dec. 17.

"We would have liked to have found a most probable cause by now" for the cracks that were found on Discovery's fuel tank, said Bill Gerstenmaier, head of NASA's space operations.