Tensions are high in the South China Sea as the Philippines kicks off its annual Balikatan joint military exercises with the United States. The opening ceremony of the three-week, 17,000-troop operation took place on Tuesday, aimed at “highlighting [the] ironclad alliance” between Washington and Manila, according to the U.S. Indo-Pacific Command. The exercises will also include France and Australia.

In response, China is signaling its own regional relationships. Chinese Foreign Minister Wang Yi was in Cambodia on Monday. His Cambodian counterpart, Chenda Sophea Sok, told reporters that his government doesn’t appreciate “troublemaking in the region by extraterritorial forces.”