CNN — Secretary of State Antony Blinken on Tuesday reiterated the United States’ “ironclad commitment” to defend the Philippines as rising tensions with China in the South China Sea raise fears of a broader regional conflict.

Stability in the region is seen as being increasingly threatened by clashes between Chinese coast guard and maritime militia units and Philippine vessels around disputed features in the waterway. In the most recent confrontation two weeks ago, a Chinese coast guard vessel used a water cannon against a Philippine boat, shattering its glass panel and injuring four Filipino sailors.

Speaking at a joint news conference with his Philippine counterpart in Manila, Blinken said the allies “have a shared concern about the PRC’s (People’s Republic of China) actions that threaten our common vision for a free, open Indo-Pacific, including in the South China Sea and in the Philippines’ exclusive economic zone.”

“Repeated violations of international law and the rights of the Philippines – water cannons, blocking maneuvers, close shadowing, other dangerous operations – these waterways are critical to the Philippines, to its security, to its economy, but they’re also critical to the interests of the region, the United States, and the world,” he said.

The US military maintains a regular presence in the South China Sea, with aircraft overflights, so-called freedom of navigation operations, and patrols and exercises with allies and partners to assert that the sea is an international waterway.

Blinken said a mutual defense treaty signed in 1951, under which Washington is bound to defend Manila from attack, is “ironclad” and “extends to armed attacks on the Filipino armed forces, public vessels, aircraft – including those of its coast guard – anywhere in the South China Sea.”

“Most important is we stand together in our determination to uphold international law – for the Philippines, for everyone else – against any provocative actions,” he said.

The “extraordinary expansion” of ties between the US and the Philippines had been in “hyperdrive” in recent months, Blinken said. But the closer partnership was not aimed at any country, the top US diplomat and Philippine Secretary of Foreign Affairs Enrique Manalo insisted.

The Philippine official also stressed that Manila aimed to resolve disputes through peaceful diplomacy.

“The Philippines has always maintained the policy of addressing any disputes and managing them through diplomatic means and through peaceful means, and we are still committed to that,” Manalo said.

China claims “indisputable sovereignty” over almost all 1.3 million square miles of the resource-rich South China Sea, despite a 2016 ruling to the contrary by an international tribunal in The Hague.

“The US is not a party to the South China Sea issue and has no right to interfere in the maritime issues between China and the Philippines,” Chinese Ministry of Foreign Affairs spokesperson Lin Jian said in a regular press conference Tuesday.

Philippine President Ferdinand Marcos Jr. has openly aligned with the US since winning power in 2022 in a shift from his predecessor’s closer relationship with Beijing – and has taken a stronger line on criticizing China’s actions in the South China Sea.

Tuesday marked Blinken’s second visit to Manila since Marcos took office, and comes weeks before President Joe Biden is set to host the Philippine president and Japanese Prime Minister Fumio Kishida at a White House summit in April.

Blinken described the upcoming summit as a “new horizon of cooperation” that is “incredibly promising,” in remarks before he met with Marcos on Tuesday.

“It’s building on the very strong foundation between our countries, where we have the same priorities, whether it’s economic development, whether it’s dealing with climate change, with food security, of course upholding international law – all of these things are front and center,” Blinken said.

In a statement Monday, White House spokesperson Karine Jean-Pierre said the three leaders “will discuss trilateral cooperation to promote inclusive economic growth and emerging technologies, advance clean energy supply chains and climate cooperation, and further peace and security in the Indo-Pacific and around the world.”

 CNN’s Manveena Suri and Wayne Chang contributed reporting.