MANILA: The United States, Australia, Japan and the Philippines will hold joint naval and air operations in the disputed South China Sea on Sunday, their defence chiefs said in a statement, as they seek to counter China's growing assertiveness in the region."Demonstrating our collective commitment to strengthen regional and international cooperation in support of a free and open Indo-Pacific, our combined defense/armed forces will conduct a Maritime Cooperative Activity within the Philippine Exclusive Economic Zone on April 7, 2024," they said in a joint statement.