Japan will send ships to the Middle East to protect commercial oil vessels - but not as part of the US-led coalition.
Japan will not join a US-led coalition to protect commercial vessels in the Middle East, but is preparing to send its own force to ensure the safe shipment of oil supplies to Japan.
Chief Cabinet Secretary Yoshihide Suga said that Japan will keep cooperating closely with Washington even if it won't join the initiative the US says is aimed at protecting commercial tankers from alleged Iranian attacks.
"Peace and stability in the Middle East is extremely important for the international society, including Japan," Mr Suga said at a news conference on Friday.
"After we studied comprehensively what measures can be most effective, we have decided to pursue our own measures separately."
The Australian Defence Force will contribute about 200 troops, a surveillance plane and a warship to the US-led cause.
Japan's energy needs rely heavily on oil imports. It has kept friendly ties with Iran and is reluctant to join such a force.
Japanese Prime Minister Shinzo Abe has tried to help ease tension between Washington and Tehran.
US-Iranian relations have deteriorated since President Donald Trump last year pulled out of the 2015 nuclear deal between Iran and world powers and re-imposed sanctions that deteriorated the Iranian economy.
Iran has since begun breaking terms of the deal, with tensions including the seizure of oil tankers at sea.
Mr Suga said Japan plans to deploy warships initially for information gathering purposes to the Gulf of Oman, the Northern Arabian Sea and nearby waters, but did not include the Strait of Hormuz at the centre of the US-Iran tension.
Sending warships to areas of military tension is a highly sensitive issue in Japan, where its pacifist postwar constitution strictly limits use of force to the country's self-defence only.
Prime Minister Shinzo Abe, however, has gradually expanded Japan's military role.
In June, a Japanese-operated tanker was attacked in the Gulf of Oman, for which Washington said Iran was responsible and urged Japan to join the US-led military initiative.