THE BRP SIERRA MADRE, a marooned transport ship which Philippine Marines live in as a military outpost, is pictured in the disputed Second Thomas Shoal, part of the Spratly Islands in the South China Sea. 鈥 REUTERS

THE UNITED STATES on Saturday called on China to stop harassing Philippine vessels in the South China Sea, pledging to stand with the Philippines at a time of simmering geopolitical tension.

鈥淲e call upon Beijing to desist from its provocative and unsafe conduct,鈥 the US State Department said in a statement.

It said China鈥檚 action was an 鈥渋nfringement upon freedom of navigation鈥 in the waterway. 鈥淚magery and video recently published in the media is a stark reminder of [Chinese] harassment and intimidation of Philippine vessels as they undertake routine patrols within their exclusive economic zone.鈥

The Philippines on Friday accused China鈥檚 coast guard of 鈥渁ggressive tactics鈥 after an incident during a Philippine Coast Guard patrol close to the Philippine-held Second Thomas Shoal, a flashpoint for previous altercations located 105 nautical miles (195 km) off its coast.

Second Thomas Shoal is home to a small military contingent aboard a rusty World War II-era US ship that was intentionally grounded in 1999 to reinforce the Philippines鈥 territorial claims.

In February, the Philippines said a Chinese ship had directed a 鈥渕ilitary-grade laser鈥 at one of its resupply vessels.

China claims sovereignty over almost the entire South China Sea based ona 1940s nine-dash line map. It鈥檚 expansive claims stretch more than 1,500 km off its mainland and cuts into the exclusive economic zones of Vietnam, the Philippines, Malaysia, Brunei and Indonesia.

A United Nations-backed international arbitral ruling in 2016 dismissed that line as having no legal basis.

China鈥檚 Foreign Ministry on Friday said the Philippine vessels had intruded into Chinese waters and made deliberate provocative moves.

The State Department said Washington 鈥渟tands with our Philippine allies in upholding the rules-based international maritime order and reaffirms that an armed attack in the Pacific, which includes the South China Sea, on Philippine Armed Forces, public vessels, or aircraft, including those of the Coast Guard, would invoke US mutual defense commitments under Article IV of the 1951 US-Philippines Mutual Defense Treaty.鈥

The US State department was referring to the near-collision incident between鈥 a Chinese coast guard ship and a Philippine patrol vessel carrying journalists on April 23.

It happened just a day after Chinese Foreign Minister Qin Gang met with President Ferdinand R. Marcos, Jr. in Manila where they agreed to establish more 鈥渓ines of communications.鈥

Boosting communication lines between the two countries would help immediately resolve 鈥渁ny event that occurs in the West Philippine Sea that involves China and the Philippines,鈥 Mr. Marcos said in a statement after their meeting.

The incident happened after BRP Malapascua and BRP Malabrigo of the Philippine Coast Guard approached Second Thomas Shoal, which the Philippines calls Ayungin.

The Philippine vessels were shadowed by Chinese Navy and coast guard ships while these were patrolling within the Philippines鈥 exclusive economic zone in the South China Sea.

The Philippine Coast Guard said it had spotted a swarm of more than 100 Chinese vessels during the April 18- 24 journey.

鈥淚t appears that the Philippines is being inexorably sucked into a dangerous military response to the alarming crisis in the West Philippine Sea,鈥 Temario C. Rivera, a retired professor of international politics at the University of the Philippines, said.

鈥淭his is the classic dilemma of an immovable object being pressured by a relentless force,鈥 he said in a Facebook Messenger chat. 鈥淢ore than ever, it is time to take seriously a political and diplomatic response to the crisis that avoids the real risk of a war in the region.鈥

Robin Michael Garcia, who teaches political economy at the University of Asia and the Pacific, said Washington鈥檚 statement 鈥渉elps rebuild the decreased trust toward the US alliance in the Philippines and in Asia.鈥

鈥淎s long as there鈥檚 a constructive conversation between the Philippines and China amid the renewed US position in Asia, conflict may be put at bay,鈥 he said.

Mr. Marcos on Sunday left Manila for Washington, where he is expected to meet with President Joseph R. Biden and talk about ways to enhance the two countries鈥 alliance.

The White House on April 21 said Mr. Biden would reaffirm the US鈥 ironclad commitment to the defense of the Philippines. They will discuss efforts 鈥渢o strengthen the longstanding US-Philippine alliance.鈥 鈥 Kyle Aristophere T. Atienza with Reuters