A Japanese warship is to take part in a multinational exercise in the South China Sea for the first time, but officials in Tokyo insist the Kunisaki's involvement is purely in a disaster-relief capacity.
The Maritime Self-Defence Force (MSDF) ship left the US Navy's Yokosuka Base, southwest of Tokyo, yesterday.
The Kunisaki is due to arrive in Vietnam next Friday for 11 days of exercises.
The ship will be used to transport as many as 140 US and Australian troops that are also taking part in the Pacific Partnership drills, which were first held in 2007 and are led by the US.
It is the largest number of foreign troops that an MSDF vessel has transported as part of the annual exercises.
The 9,000-tonne Kunisaki is officially categorised as a tank landing ship.
"Our participation is based on a peacekeeping and international disaster-relief scenario," a spokesman for Japan's Ministry of Defence said. "It is not a military exercise. The aim is to enhance our capabilities in providing medical care and transportation facilities."
After taking part in the drills off Vietnam, the Kunisaki will go on to Cambodia for nine days from June 19 and the Philippines from July 4 to 15.
The joint exercises are ostensibly disaster-relief drills, but it will not have gone unnoticed in the region that they bring together several nations locked in territorial disputes with China.
"This will be taking place in a region that is very sensitive at the moment," said Masayuki Masuda, a China expert at Japan's National Institute of Defence Studies.
"But the feeling is that China cannot express any opposition because these vessels are practicing the provision of humanitarian assistance in the event of a natural disaster or some other form of crisis.
"While this is not a traditional war-based scenario, it does also serve to make clear the multinational support that exists in the region and our efforts to ensure regional security."