The Bush administration has authorized the sale of 40 naval surface-to-air missiles to Japan, saying its ally needs the weapons to defend vital sea lanes.

The SM-2 Block IIIB missiles are carried on warships and can shoot down incoming missiles and aircraft.

The total value of the deal, which would include technical support and other associated parts, could be as high as $104 million, according to a statement from the Pentagon's Defense Security Cooperation Agency.

The sale won't affect the basic military balance in the Western Pacific, the agency said in a press release. Japan's potential adversaries include North Korea (search) and China, which have large militaries.

The main contractors on the deal are Raytheon outlets in Tucson, Ariz. and Camden, Ark. and United Defense outlets in Minneapolis and Aberdeen, S.D., the agency said.

"Japan is one of the major political and economic powers in East Asia and the Western Pacific and a key ally of the United States in ensuring the peace and stability of this region," the agency said in its statement. "The SM-2 missiles will be used on ships of the Japan Maritime Self Defense Force fleet and will provide enhanced capabilities in providing defense of critical sea-lanes of communication."

Congress has a month to pass a joint resolution opposing such a sale, which would effectively kill it. Such a move is regarded as unlikely.