Prime Minister Shinzo Abe and his visiting Australian counterpart, John Howard, signed a landmark security accord Tuesday to strengthen bilateral cooperation, making Japan Australia's closest security ally after the United States.

For Japan, the pact is the first modern diplomatic arrangement on permanent security cooperation with a country other than the U.S.

Aware that the deal could irk China, the two leaders have expressly denied the pact is intended to contain Japan's giant neighbor, whose military presence is growing in the Asia-Pacific region.