Damage to Philippine vessels and injuries to their crew in the South China Sea is “irresponsible behavior” in disregard of international law, U.S. Defense Secretary Lloyd Austin said Thursday in Honolulu, weighing in on the latest flare-up involving China.

Manila and Beijing have traded barbs almost daily since Tuesday’s confrontation at the disputed Scarborough shoal, where China’s coast guard used water cannons against two vessels from the Philippines, prompting outrage from its government.

“We’ve been very clear to everyone, to include Beijing, that the kind of behavior we’ve seen, where Filipino crews are put in danger… sailors have been injured and property damaged, that is irresponsible behavior,” Austin told a joint news conference in Honolulu.

Austin reiterated the United States would continue to support its former colony the Philippines, as outlined in a 1951 Mutual Defense Treaty.

“Our commitment to the treaty is ironclad and we stand with the Philippines,” he said after a meeting with defense counterparts of the Philippines, Australia and Japan.

Teodoro refused to speculate about the conditions in which Manila might invoke the treaty, saying that would be a “political decision”.

The treaty binds the two countries to defend each other in the event of an attack, including in the South China Sea, upping the stakes in a long-running battle for power that has seen China double down in asserting its territorial claim over most of the waterway, a key global trade route.

Appearing alongside Austin, Philippine Defence Secretary Gilberto Teodoro said the two were committed to building capacity and deterrence to ensure no situation emerged that would require the treaty to be invoked.

“We need to assert our rights but in a manner that safeguards the safety of each and every member of the Philippines’ armed force,” he added.

The Scarborough Shoal, a prime fishing patch used by several countries, has been occupied by China for more than a decade and has been flashpoint between the Philippines and China on and off for years.

China this week accused the Philippines of encroachment and warned it not to challenge its resolve to defend its sovereignty.

Tensions between them have escalated elsewhere in the South China Sea recently as the Philippines steps up its coast guard patrols near disputed features within its exclusive economic zone, while strengthening alliances with the United States and Japan, moves Beijing sees as provocations.

Two Philippine vessels suffered damage from water cannon use late last month, while at least four crew members were injured in a similar incident in March.