CNN  — 

China is facing a growing international backlash after one of its coast guard vessels used a water cannon against a Philippine boat in the South China Sea on Saturday, an incident analysts say escalates an already tense situation and could see the United States and its allies speed up plans for joint patrols in the waterway.

Video from the Philippines showed a large Chinese Coast Guard ship spraying a much smaller Philippine boat that was attempting to deliver supplies to a garrison of Philippine marines on Second Thomas Shoal, a South China Sea feature in Manila’s exclusive economic zone that China calls Renai Reef and also claims as its sovereign territory.

Images from the Philippine Coast Guard also showed the Chinese ship moving dangerously close in front of the Philippine Coast Guard vessels as they escorted the resupply boats.

“The Philippine Coast Guard (PCG) strongly condemns the China Coast Guard’s (CCG) dangerous maneuvers and illegal use of water cannons against PCG vessels,” the PCG wrote in a statement shared on its official Facebook account Saturday.

By Sunday, Manila’s main ally, Washington, condemned the Chinese actions and reiterated that it would meet its mutual defense treaty obligations with the Philippines.

“The United States reaffirms an armed attack on Philippine public vessels, aircraft, and armed forces — including those of its Coast Guard in the South China Sea — would invoke US mutual defense commitments under Article IV of the 1951 US Philippines Mutual Defense Treaty,” US State Department spokesperson Matthew Miller said in a statement.

US allies joined in a united front with Washington and Manila.

Australia, Japan and Germany called the Chinese actions “dangerous” and “destabilizing.”

And the Canadian Embassy in Manila said Ottawa “unreservedly condemns the dangerous and provocative actions taken by the Chinese Coast Guard.”

The Philippines has accused Chinese Coast Guard ships of firing water cannons and making "dangerous maneuvers" at its ships in the South China Sea.

Philippine President Ferdinand Marcos Jr. said on Monday his foreign affair secretary delivered a diplomatic note of complaint “along with images and videos on what had happened” to the Chinese ambassador in Manila.

Meanwhile, the Philippine Foreign Ministry and armed forces held a joint press conference condemning what they called China’s “dangerous and illegal practice” of using water canon, saying the action put “the lives of the Filipino crew at risk in violation of humanitarian and international law.”

Longstanding dispute

The South China Sea has long been a source of tension between Manila and Beijing.

Beijing claims “indisputable sovereignty” over almost all of the 1.3 million square mile South China Sea, as well as most of the islands within it, even those hundreds of miles from the Chinese mainland.

That includes the Spratlys, which Beijing calls the Nanshas, an archipelago consisting of 100 small islands and reefs also claimed in full or part by the Philippines, Malaysia, Brunei and Taiwan.

Manila, however, calls the area the West Philippine Sea. In 1999 it intentionally grounded a navy transport ship, the BRP Sierra Madre, on Second Thomas Shoal, manned by Filipino marines, to enforce the country’s claim to the area.

Manila’s claims are backed by the international Permanent Court of Arbitration in the Hague, which ruled in 2016 that China has no legal basis to claim historic rights to the bulk of the South China Sea.

Beijing has ignored the ruling.

Analysts and Philippine politicians called Saturday’s incident a step up from a string of Chinese-Philippine confrontations this year, including a Chinese ship aiming a laser at a Philippine vessel in February and then a series of close encounters analyst Collin Koh called “near collisions.”

“Clearly this latest incident represents an escalation,” said Koh, research fellow at the S. Rajaratnam School of International Studies in Singapore.

m”I really believe we’re entering the period of brinkmanship diplomacy,” Philippine Sen. Alan Peter Cayetano told CNN affiliate CNN Philippines.

“If something goes wrong, it can really cause instability in the region,” he said.

But China shows no sign of backing off its claims.

“Two Filipino supply vessels and two coast guard