In the first sale of full defense equipment under Japan's "three principles of arms transfer," approved in 2014, Mitsubishi Electric Co. will sell four air defense radar systems to the Philippines, sources said.

Mitsubishi Electric won a bid to export the improved version of the three J/FPS-3 and one J/TPS-P14 air defense systems, which are used by the Self-Defense Forces.

The former has been placed in the mountains along coastal areas in Japan to detect incoming fighter jets or missiles. The system has been used as a missile defense system against North Korea and for other purposes.

The latter can be loaded on a truck and other locations to detect incoming aircraft or helicopters.

Four export contracts have been made under the Abe administration's Three Principles on Transfer of Defense Equipment and Technology, which allows arms exports with conditions.

But the items were limited to parts, such as sensors for PAC-2 surface-to-air missiles manufactured by Mitsubishi Electric.

The Philippines government had approached the United States and other countries about purchasing air defense radar systems, sources said.

Mitsubishi Electric was notified of the selection in March. The company is expected to receive the formal order by May, for a total amount of about 10 billion yen ($90 million).

The Philippines faces the South China Sea, which is an important shipping route for Japan. But in recent years, China's military has increased its stronghold and influence over the region.

The National Security Council has apparently approved the export of an air defense radar system to the Philippines as a deterrent against China.

Mitsubishi Electric’s successful bid was a result of sales efforts made by the public-private partnership, sources said.

The administration of Prime Minister Shinzo Abe in April 2014 adopted the three principles at a Cabinet meeting, replacing the Three Principles on Arms Exports, which had banned the export of arms.

The new principles allow arms exports as long as such a transfer is deemed “contributing to international peace” and “benefiting national security” among other conditions.

With the change, the administration aims to work with other countries to develop arms to enhance national security, reduce defense costs and strengthen the Japanese defense industry.

Japan has signed an agreement to make that possible with nine countries including the United States, Britain and Australia.