The United States said Monday that it stood by its Philippine ally and emphasized their mutual defense treaty after vessels from China and the Philippines clashed amid heightened tensions in the disputed South China Sea.

Earlier, the Chinese foreign ministry urged Manila not to challenge Beijing’s efforts to “safeguard its territorial sovereignty and maritime rights and interests” after Sunday’s incident in the Spratly Islands, in which the Philippines said China deployed water cannon and rammed a Filipino vessel.

State Department spokesperson Tommy Pigott condemned China’s “ramming and water cannoning” of a Philippine vessel and said Washington stood with its ally “as they confront China’s dangerous actions which undermine regional stability.”

In a statement, Pigott reaffirmed that Article IV of the 1951 U.S. Philippines Mutual Defense Treaty “extends to armed attacks on Philippine armed forces, public vessels, or aircraft — including those of its Coast Guard — anywhere in the South China Sea.”

China and the Philippines have traded accusations over the confrontation near Sandy Cay, a coral reef within the Spratly Islands.

The two nations have confronted each other repeatedly in recent years in the South China Sea, a strategic trade route that facilitates more than $3 trillion in annual ship-borne commerce, and which China claims most of.

Tensions have heightened recently and Lin Jian, a spokesperson for the Chinese foreign ministry, told a regular news briefing that the Philippines should immediately stop “violations and provocations.”

The State Department said: “China’s sweeping territorial and maritime claims in the South China Sea and its increasingly coercive actions to advance them at the expense of its neighbors continue to undermine regional stability and fly in the face of its prior commitments to resolve disputes peacefully.”

Last year, during the former Biden administration, two senior Republican U.S. senators called for a list of options developed by the Pentagon and State Department to support the Philippines against Beijing in the South China Sea, saying that limiting responses to verbal assurances of the applicability of Article IV undermines the credibility and value of these commitments.