Japan has deployed a warship to critical oil shipping lanes in the Middle East, and has authorized use of force for those ships, Reuters reported on Sunday. The decision to authorize force in order to protect ships in danger is a controversial one, according to Reuters, because Japan’s constitution forbids the use of military force in international disputes. But the situation is a dire one, with 90% of all of Japan’s oil coming from the Middle East. “Thousands of Japanese ships ply those waters every year including vessels carrying nine tenths of our oil. It is Japan’s lifeline,” Japanese Prime Minister Shinzo Abe told the crew of the destroyer Takanami prior to departure.

The destroyer will head to the Gulf of Oman, and will patrol there as well as in the northern Arabian Sea and the Gulf of Aden. It will not, however, patrol the Strait of Hormuz—the world’s most critical and risky oil chokepoint in the world, after Iran repeatedly threatened to close the Strait and hijacked oil tankers in the Strait last year.

Japan is acting to protect its oil interests in the region, but it is also being cautious. Japan has a fairly stable relationship with Iran and has strong ties to the United States and other allies who are also patrolling the area. Japan will not collaborate with these allies, nor does it seek to provoke Iran by its presence in the area.

Japan’s oil tanker the Kokuka Courageous was attacked in June in the Gulf of Oman near the Strait of Hormuz. Japan condemned the attack on its tanker, but while the US blamed the incident on Iran, Japan stopped short of doing so. The Takanami will also be accompanied by two patrol planes.