MANILA, March 13 (Reuters) - The Philippines is planning another challenge of a Chinese naval blockade of a disputed shoal in the South China Sea by sending civilian ships with supplies to its troops stationed there, a senior military official said on Thursday.
Chinese coastguard ships patrolling waters around Second Thomas Shoal, known in China as the Ren'ai reef and in the Philippines as Ayungin, ordered the same vessels to leave the area on Sunday.
Beijing claims Manila is trying to start construction on the disputed reef after it ran aground an old transport ship in 1999 to mark its territory and stationed marines on the ship. Manila claims the shoal is part of the Philippine's continental shelf.
"We are on a humanitarian mission," said a marine colonel, who declined to be identified because he was not authorised to speak to the media. "We are sending back the civilian ships to bring food and fresh water because they are running out of supplies. Fresh water supply is critically low."
On Monday, the Philippine navy air-dropped food and water to soldiers stationed on the grounded transport ship. The fresh water supply is good only for three to four days, the colonel said.
China says Manila is planning to build a permanent structure on the shoal, which Beijing claims to be part of its territory based on its historical nine-dash-line claims. The Philippines denies Beijing's assertion.
"We are abiding by the rules, or by the agreement that there will be no construction," he said. "Those are mere items for improvement of the living conditions of our men there."
On Tuesday, Manila summoned the second highest Chinese embassy official, calling the blockade "a clear and urgent threat to the rights and interests of the Philippines".
Beijing's claim over islands, reefs and atolls that form the Spratlys, a group of 250 uninhabitable islets spread over 165,000 square miles, has set it directly against U.S. allies Vietnam and the Philippines, while Brunei, Malaysia and Taiwan also lay claim to parts of the South China Sea.
The United States says it is troubled by China's blockade, calling it a "provocative move". China's Foreign Ministry on Thursday criticised Washington for getting involved.
"The U.S. statement ... does not accord with its status as a non-involved country, violates the United States' promise to not take a stance on the dispute, brings a negative influence to safeguarding the peace and stability of Southeast Asia, and finally, does not accord with its own interests," Foreign Ministry spokesman Qin Gang said.
"China has the right to drive away the Philippines' two ships," Qin said in a statement posted to the ministry's website, adding that the Philippines had violated a promise made years ago to tow away the beached ship.
Second Thomas Shoal, a strategic gateway to Reed Bank, believed to be rich in oil and natural gas, is one of several possible maritime flashpoints that could prompt the United States to intervene in defence of Asian allies troubled by increasingly assertive Chinese maritime claims.
The South China Sea provides 10 percent of the global fish catch, carries $5 trillion in ship borne trade a year and its seabed is believed to be rich with energy reserves. (Reporting By Manuel Mogato and Michael Martina in BEIJING; Editing by Jeremy Laurence)