The defense ministers of Japan, the United States, Australia and the Philippines on Thursday expressed their "serious concern" over China's recent "dangerous and destabilizing conduct" against Philippine vessels in the South China Sea.
In a joint readout issued after their talks in Hawaii, the four ministers urged China to adhere to a 2016 ruling by an international court that invalidated its claim of sovereignty over almost the entire South China Sea, amid Beijing's growing assertiveness in regional waters.
In the latest flare-up, Chinese coast guard ships used water cannons against Philippine vessels in March and April near disputed shoals in the resource-rich South China Sea.
Chinese vessels have also repeatedly entered Japanese territorial waters around the Senkaku Islands, a group of Tokyo-administered uninhabited islets in the East China Sea that Beijing claims and calls Diaoyu.
The defense ministers pledged to maintain the rules-based order in the Indo-Pacific region at a joint press conference, and shared an understanding about the importance of coordinated activities by the four nations, including joint naval drills in the regional waters.
The four agreed to continue their forces' joint exercises in the South China Sea, according to Japan's Defense Ministry.
"We've gathered here because we share a vision for peace, stability and deterrence in the Indo-Pacific," U.S. Defense Secretary Lloyd Austin told the news conference.
Japanese Defense Minister Minoru Kihara stressed that it is "an urgent issue" for the four countries to work together with other like-minded states to that end.
The talks in Honolulu came as Washington and the three U.S. allies have been stepping up bilateral and multilateral security collaboration in recent years in an apparent show of unity against China's intensifying military activities in regional waters.
In July 2016, the Permanent Court of Arbitration at The Hague ruled out China's rights to resources in the South China Sea based on its expansive, self-proclaimed "nine-dash line."
Last month, the four nations conducted their first full-scale joint naval exercises in the South China Sea, dubbed "the Maritime Cooperative Activity," to demonstrate the "collective commitment to strengthen regional and international cooperation in support of a free and open Indo-Pacific."
Austin said Thursday that such training serves to "build bonds among our forces" and "underscore our shared commitment to international law in the South China Sea," adding that the countries are "looking to conduct more maritime exercises and activities."
In a thinly veiled reference to China, Kihara said the four ministers "stand united to strongly oppose any attempt to unilaterally change the status quo of the South China Sea by force or any activity to heighten the tension in the region."
Without naming China, Australian Defense Minister Richard Marles said the global rules-based order is "under intense pressure" and the latest gathering sends "a very significant message to the region and to the world about four democracies which are committed to the global rules-based order."
Philippine Defense Secretary Gilberto Teodoro welcomed the strengthened quadrilateral ties aimed at not only protecting his nation's territorial integrity and sovereignty but also upholding "principles of international law which guide the global order in the proper way that nations should live amongst each other."
It is the second defense ministerial gathering for the four Pacific Rim countries. In June last year, their defense chiefs held their first-ever quadrilateral meeting in Singapore on the fringes of the annual Asia Security Conference, known as the Shangri-La Dialogue.
On Thursday, Kihara met bilaterally with Austin and Marles, respectively, and the three also held trilateral talks.
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