Japanese Prime Minister Shinzo Abe may consider a request from the Philippines for large coastguard ships to patrol the disputed South China Sea, after the two allies reached a deal on defence equipment and technology.

China has overlapping claims with Brunei, Malaysia, the Philippines, Taiwan and Vietnam in the South China Sea, through which $5 trillion in ship-borne trade passes every year.

The Philippines is the Southeast Asian nation most at odds with China over the South China Sea. Tokyo has no claims in the waterway, but worries about China's growing military reach into sea lanes through which much of Japan's ship-borne trade passes.

The deal will mark the first time Japan has agreed to directly donate military equipment to another country, and is the latest example of Abe's more muscular security agenda.

"There was a request from President Benigno Aquino regarding the provision of large patrol vessels to the Philippine Coast Guard and Japan would like to consider the specifics," Abe said in a statement.

The two leaders met on Thursday night at the close of the Asia Pacific Economic Cooperation (APEC) summit in Manila.

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Abe said he welcomed the deal and "agreed to work together for the early signing of the agreement and the realization of cooperation in defence equipment".

There have been media reports that Tokyo would supply Manila with three used Beechcraft TC-90 King Air aircraft suitable for maritime surveillance in the South China Sea. Manila had also sought Lockheed Martin submarine-hunting P3-C patrol planes.

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Rather than challenge Beijing directly by sending warships or planes to patrol the South China Sea, Japan is helping to build the military capacity of friendly nations with claims to parts of the waterway.

"These negotiations take some time," a senior Japanese official told Reuters, saying it could take one or two years before the two sides sign a deal on defence equipment and technology.

"Japan wants an assurance that any equipment it will give will not be transferred to a third country."

To allow the donation, Japanese lawmakers will either have to tweak curbs on sales of government-owned equipment, or set up a separate financing mechanism.

Japan is also building 10 40-metre (131-ft) -long vessels for the Philippine coastguard. Manila needs 100-metre (328-ft) -long patrol ships.

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Japan changed defence policy this year in a shift that could let troops fight overseas for the first time since 1945.

The move was welcomed by ally the United States, but fed concern in China, where memories of Japan's wartime aggression run deep.