The United States and Japan plan to study a joint missile defense system with Australia that would boost their security role in the Asia-Pacific region, a Japanese government source said on Tuesday.
Tokyo and Washington have already been working on a defense shield to ward off potential threats from North Korea, and the government official said the new plan also envisaged a possible firing of Chinese missiles over Australia and Guam.
A basic agreement to jointly study the missile defense system was reached in April when government officials from Japan, the United States and Australia met in Tokyo, the source said.
"The basic tenet of the plan is to step up cooperation between the three countries in the field of security in the Asia-Pacific region," the source, who declined to be identified, told Reuters.
The source declined to say whether Australia would go ahead and introduce a missile defense system.
"But Australia appears quite willing to contribute to maintaining security in the region and the joint study programme was worked out to deal with the changing security situation in the region," he said.
The United States and Japan started planning a missile defense system after North Korea test-fired a ballistic missile, part of which flew over Japan and landed in the Pacific Ocean, in 1998.
Japan speeded up implementation of its missile defense programme after North Korea fired a volley of missiles last July.
Officials from the three countries are expected to meet and discuss the project later this year, the source said.
In March, Japan and Australia signed a ground-breaking defense pact that the leaders of both countries stressed were not aimed at reining in China.
Japan's first such pact with a country other than the United States sets priorities for security cooperation in areas such as counter-terrorism, maritime security, border protection and disaster relief.
As the United States' most loyal allies in the Asia-Pacific region, Japan and Australia sent troops to Iraq, and the three countries have already tightened ties through regular talks.