The Air Force may need an estimated $8 billion to upgrade the technology of the B-1 bomber to meet the threat of increasingly sophisticated Soviet air defenses, it was reported Tuesday.

A study by the Congressional Budget Office said the improvements are being considered only by the Air Force but must be kept in mind in deciding on the future role of the bomber.As Soviet air defense systems inevitably improve, the capability or the role of the $28 billion bomber program must as well, the non-partisan congressional research group said in a report released by the House Armed Services Committee.

The ultimate price tag for the bomber depends on whether it continues to serve its current mission - as an attack aircraft for targets inside hostile territory or as a "standoff" bomber, laden with subsonic Cruise missiles that are fired against many of the same targets.

The Air Force, with Congress looking on, is still reviewing what roles may be best suitable for the bomber, 100 of which have been deployed.

The report said "enhancements," or improvements, under consideration include technology to detect and warn against air-to-air missiles; to locate mobile missiles; upgrading radar systems to improve the bomber's ability to hug the terrain and avoid radar; to jam radar systems; night navigation; and communication.

"The enhancements, which informal estimates suggest could cost as much as $8 billion, have not yet been proposed to Congress but may well be part" of the next budget, the report said.