The Philippines and Vietnam have upgraded their relationship to an "enhanced strategic partnership" following a two-day state visit to Manila by To Lam, the leader of Vietnam's Communist Party — the first such visit by a Vietnamese party chief to the Philippines. At a joint press conference, Philippine President Ferdinand Marcos said the two nations share a commitment to "peace, stability, and a rules-based order" and reaffirmed that freedom of navigation in the South China Sea is "non-negotiable," with both sides backing the 2016 international arbitral ruling that invalidated most of China's sweeping maritime claims under the UN Convention on the Law of the Sea (UNCLOS). The upgrade, which includes a renewed defence cooperation agreement and expanded joint naval activities, comes as both countries face growing pressure from China's assertive behaviour in the South China Sea (a strategic waterway claimed largely by Beijing but also contested by several Southeast Asian nations), and ahead of the 50th anniversary of Philippine-Vietnamese diplomatic relations on 12 July.