The move comes after attacks this year on tankers in the Gulf including a Japanese tanker, as well as on Saudi Arabian oil installations.

Washington, other Western states and Saudi Arabia blame the attacks on Tehran, which denies any involvement.

Japan will send a destroyer to the region for intelligence activities along with two P3C patrol aircraft, chief cabinet secretary Yoshihide Suga, the top government spokesman, told reporters.

The move is "Japan's own measure aimed at peace and stability in the Middle East as well as ensuring safety of Japan-related vessels," Suga said, noting that 90 percent of crude oil Tokyo imports were from the region.

Middle East tensions have soared since early this year, when Iran was accused of attaching mines to several tankers off Saudi Arabia and the United Arab Emirates, and then attacking or seizing others near the crucial Strait of Hormuz.

The United States formed a naval coalition to protect vessels in the region, which is critical to global oil supplies.

Britain and Australia are the principal Western partners of the United States to have agreed to send warships to escort commercial shipping in the Gulf.

Most European countries have declined to participate, fearful of undermining their efforts to save a nuclear accord with Iran after the US withdrew last year.

The Japanese patrol activities will not be deployed in the Strait of Hormuz, through which much of the global oil trade passes and where the US-led coalition operates, a defence ministry spokesman told AFP.

The Self-Defense Forces (SDFs) will operate in the high seas in the Gulf of Oman, the northern Arabian Sea and the Gulf of Aden, he said.

Japan's post-World War II pacifist constitution commits it to strictly defensive capabilities, but Prime Minister Shinzo Abe has campaigned for years to amend it.

Japan, a close American ally, also has longstanding relations with Iran.