Japan, which is embroiled in separate territorial dispute with China in the neighbouring East China Sea, has yet to conduct a FONOP in the South China Sea
Japan's biggest warship, the Kaga helicopter carrier, joined naval drills with Britain's HMS Argyll in the Indian Ocean on Wednesday as the frigate headed toward the contested South China Sea and East Asia.
Britain, Japan and close ally the United States have found common cause in countering growing Chinese influence in the region, to keep key sealanes linking Asia to Europe, the United States and elsewhere from falling under Beijing's sway.
"We have traditional ties with the British navy and we are both close US allies and these drills are an opportunity for us to strengthen cooperation," Kenji Sakaguchi, the Maritime Self Defence Force (MSDF) commander of the Kaga group's four helicopters said on the hangar deck.
The more frequent presence of the Royal Navy is a chance for the two navies to train more closely in the future, he added.
The Argyll, Kaga and its destroyer escort the Inazuma practiced formations on calm seas in the Indian Ocean near commercial sea lanes plied by container vessels and oil tankers. Three helicopters from the Japanese carrier hovered above, monitoring the drill.
The Argyll's arrival comes after Britain's amphibious assault ship Albion last month challenged Beijing's territorial claims on its way to Vietnam from Japan by sailing close to Chinese bases in the Paracel islands in a freedom of navigation operation (FONOP).
China dispatched a warship and helicopters to counter the British presence and warned London that similar action in the future could endanger talks for a possible trade deal Britain is seeking as it prepares to leave the European Union.
In Beijing on Thursday, Defence Ministry spokesman Ren Guoqiang said China was paying close attention to Japan's activities, and opposed countries from outside the region getting involved in the South China Sea issue.
"We hope Japan does more to benefit regional peace and stability and speak and act cautiously on the South China Sea," Ren told a monthly news briefing, when asked about the Kaga.
China, which says its intentions are peaceful, claims most of the South China Sea, through which about $3 trillion worth of trade passes every year. Malaysia, Vietnam, the Philippines and Brunei also claim parts of the sea, which has oil and gas deposits and rich fishing grounds.
Japan, which is embroiled in separate territorial dispute with China in the neighbouring East China Sea, has yet to conduct a FONOP in the South China Sea.
However, in a rare announcement this month, Japan's defence ministry said one of its submarines had carried out a naval exercise in the disputed waterway with two Japanese destroyers and the Kaga, which is on a two-month deployment in the Indo-Pacific.
After crossing the South China Sea, the Argyll will operate in waters around Japan, including a stint monitoring sanctions imposed on North Korea by the United Nations to force it to abandon nuclear weapons and ballistic missiles, said a British government source, who asked not to be identified because he is not authorised to talk to the media.
The Argyll is the third Royal Navy ship in Asia's waters this year, following the tour of the Albion and another frigate.
"Normally we hold discussion with other countries before joint drills, but with the British there is no need to, so they are easy to work with," said Tatsuhiko Mizuno, an operation planning officer for the Kaga group.