Philippines defiant after Chinese blockade

The Philippine military has redeployed two supply boats to provide food to marines guarding a disputed shoal in the South China Sea after the Chinese coast guard used water cannons to forcibly turn the boats away last week.

Defence Secretary Delfin Lorenzana said the boats carrying navy personnel should reach the marines stationed at Second Thomas Shoal after an overnight trip.

Lorenzana said the boats aren't being escorted by the navy or coast guard in accordance with a request by China's ambassador to Manila, who, he said, assured him in talks over the weekend that the boats would not be blocked again.

A navy plane will fly over the remote shoal, which has been surrounded by Chinese surveillance ships in a years-long territorial standoff, when the Filipino boats reach it, the defence chief said.

The Philippines says the shoal is in its internationally recognised exclusive economic zone, but China insists it has sovereignty over the waters.

The Philippines government conveyed its outrage to China after two Chinese coast guard ships blocked the two Filipino supply boats on Tuesday and a third Chinese vessel sprayed high-pressure streams of water, forcing the boats to abort their mission.

The US later said it was standing by the Philippines "in the face of this escalation that directly threatens regional peace and stability," and reiterated "that an armed attack on Philippine public vessels in the South China Sea would invoke US mutual defence commitments" under the 1951 US-Philippines Mutual Defence Treaty.

In Beijing, Chinese Foreign Ministry spokesperson Zhao Lijian responded to the Philippine protests by saying that China's coast guard had upheld Chinese sovereignty after the Philippine ships entered Chinese waters at night without permission.

It was the latest flareup in long-simmering territorial disputes in the strategic waterway, where China, the Philippines, Vietnam, Malaysia, Brunei and Taiwan have overlapping claims. China claims virtually the entire South China Sea and has transformed seven shoals into missile-protected island bases to cement its assertions, ratcheting up tensions.

The Philippine military deliberately ran aground the Sierra Madre, a World War II-era warship provided by the US, at the submerged shoal in 1999 in a move to fortify its claim. The Sierra Madre is now effectively a shipwreck but the Philippine military has not decommissioned it. That makes the rust-encrusted ship an extension of the government and means any assault on the ship is tantamount to an attack against the Philippines.