A tense stand-off is unfolding in the South China Sea between a group of Philippine marines and several Chinese naval vessels. The confrontation occurs around a shoal, which has been occupied by the Philippines, in the disputed Spratly Islands. This confrontation in the South China Sea takes place as tensions continue to simmer between Taiwan and the Philippines over the latter’s killing of a Taiwanese fisherman.

The Philippine marines are occupying a former US tank-landing vessel, the BRP Sierra Madre, which was deliberately scuttled by the Philippine Navy on the shoal in 1999 an attempt to construct a small naval outpost on the cheap. The shoal, alternately known as Ayungin, Second Thomas, or Ren’ai in China, is located 105 nautical miles from the nearest island of the Philippines, Palawan.

The Spratly Islands, of which Ayungin shoal is part, are claimed by China, Taiwan, Vietnam and the Philippines. The Spratlys are at the center of one of the busiest and most vital sea-lanes in the world.

The rusted hull of the Sierra Madre has been occupied by Philippine marines for over a decade now. On average, 10 soldiers, armed with machine guns are stationed on the make-shift base, rotated out occasionally. The station exists for the sole purpose of staking the claim by the Philippines to the oil-rich and strategically-vital surrounding waters.

Over the course of ten years, the Sierra Madre has been gradually wasting away and if it is not shored up will sink into the South China Sea. The Philippine Armed Forces, at President Aquino’s instructions have begun carrying fresh construction supplies to the location, building a fresh platform over the decrepit framework.

On May 9, the Philippine navy announced that it had spotted Chinese vessels in the vicinity of Ayungin shoal and sent its own ships to investigate. On May 18, they announced that they were sending three patrol ships to the area to prevent the Chinese vessels from returning. Subsequent reports indicated that armed Chinese naval ships had surrounded the shoal.

The Philippine navy has been for the past week unable to resupply the small group of Marines on Ayungin shoal. No account of a successful visit by a Philippine ship has yet been reported in the press.

This could evolve into another sharp standoff between Beijing and Manila, following last year’s over Scarborough Shoal, in which China claimed to have brought it under its “effective control” by deploying maritime policing vessels to keep Philippines government and fishing ships out of the reefs. Beijing is employing the same tactic to “retake” the Second Thomas.

President Aquino issued a statement asserting that this spit of coral in the Spratly Islands was an “integral part” of the Philippines. Hong Lei, spokesman for the Chinese foreign ministry, responded, declaring that Beijing has “indisputable sovereignty” over the shoal. He added that “Chinese ships are entitled to regularly patrol there.”

Washington stepped very strongly into the midst of the tense armed stand-off by dispatching the USS Nimitz, a massive nuclear-powered aircraft carrier to the South China Sea, sailing from South Korea, to Phuket in Thailand. The intervention of Washington was a calculated provocation, a display of military might pointedly targeted at China.

The US intervention underscores the fact that the Philippines, is only able to engage in these dangerous confrontations with Beijing, because of Washington’s backing and encouragement. During last year’s standoff over Scarborough Shoal, the Obama administration indicated its support to Manila under the 1951 US-Philippines mutual defense treaty.

Backing Philippines against China is part of Obama’s “pivot” to Asia aimed at containing China diplomatically, economically and strategically. South East Asia is a vital component of the Pentagon’s war plans, which include a potential blockade of China by cutting off its main shipping routes for raw materials and oil from the Middle East and Africa.

China responded to the US navy presence with its own display of force. The Chinese People’s Liberation Army (PLA) announced a joint exercise of its three naval—North, East, and South Sea—fleets. The drill was held in the South China Sea and included warships, submarines and warplanes. Retired PLA Colonel Yue Gang told the hard-line government-owned paper, Global Times, “The joint military drill also meant to tell the Philippines that Beijing’s tough stance towards them will continue.”

The Philippine government responded with bluster. A Department of Foreign Affairs spokesperson, Raul Hernandez, announced that China was in “violation of international law.” The Philippine Defense Secretary, Voltaire Gazmin, stated, “To the last soldier standing, we will fight for what is ours.”

President Aquino announced that the Philippines would be spending $US1.82 billion to modernize its military to defend the Philippines against what he termed “bullies entering our backyard.” This comment is directly referencing China, and to a lesser degree, Taiwan.

The stand-off in the Spratly Islands between the Philippines and China occur s at the same time as ongoing tensions between the Philippines and Taiwan. Taiwan has placed an embargo on granting visas to any Filipino workers attempting to enter the country, in response to a Taiwanese fisherman, shot dead in disputed waters by the Philippine coast guard earlier this month . (See: “Taiwan stages naval drills as tensions mount with Manila”)

Relations between the Philippines and Taiwan have greatly soured as a result of these events and Beijing sees in this rift an opportunity to establish closer ties with Taipei. Washington did not want to see any deterioration of relations between Taiwan and Philippines that would strengthen China’s position in the South China Sea.

With calls from the US State Department and members of the Congress for two US allies to settle the disputes, both countries are currently investigating the affair. Official investigation teams from Taipei and Manila have exchanged visits, and there is reportedly footage of the shooting which the Philippine government has supplied to the Taiwanese government.