MANILA, Philippines >> U.S. forces are obliged to help defend Filipino troops, ships or aircraft under a 1951 Mutual Defense Treaty if they come under attack in the disputed Spratly Islands in the South China Sea, Philippine officials said, citing past American assurances.

The potentially oil- and gas-rich Spratly Islands have long been regarded as one of Asia’s possible flash points for conflict. China, the Philippines and Vietnam have been trading barbs and diplomatic protests recently over overlapping territorial claims, reigniting tension.

Complicating the issue is the role the United States could play in resolving the disputes. A Mutual Defense Treaty signed by U.S. and Philippine officials in Aug. 30, 1951, calls on each country to help defend the other against an external attack by an aggressor in their territories or in the Pacific region.

Amid renewed tensions in the Spratlys, questions have emerged whether the treaty would apply if ill-equipped Philippine forces come under attack in the islands, all of which are claimed by China. Parts also are claimed by Brunei, Malaysia, the Philippines, Taiwan and Vietnam.

The Philippine Department of Foreign Affairs said in a policy paper that the treaty requires Washington to help defend Filipino forces if they come under attack in the Spratlys, citing U.S. diplomatic dispatches that defined the Pacific region under the treaty as including the South China Sea. The South China Sea was not specifically mentioned in the pact.

A copy of the policy paper was seen by The Associated Press on Wednesday.

Philippine Foreign Secretary Albert del Rosario also said in a recent interview that American officials have made clear that Washington would respond in case Filipino forces come under attack in the South China Sea.

The U.S. Embassy in Manila declined to discuss details of when the pact would apply.

"As a strategic ally, the United States honors our Mutual Defense Treaty with the Philippines," said Alan Holst, acting public affairs officer at the embassy. "We will not engage in discussion of hypothetical scenarios."

The defense treaty, which came into force in 1952, defined an attack as an armed assault on "the metropolitan territory of the parties" or their "armed forces, public vessels or aircraft in the Pacific."

While the U.S. has a policy of not interfering in territorial disputes, the Philippine paper said "it may be construed that any attack on our vessels, armed forces or aircraft in the Spratlys would make the treaty applicable and accordingly obligate the U.S. to act to meet the common dangers."

China has urged the United States to stay out of the territorial disputes in the South China Sea, saying they should be resolved through bilateral negotiations.

On Wednesday, Chinese Vice Foreign Minister Cui Tiankai warned that Washington risks getting drawn into a conflict should tensions in the region escalate further.

Washington views the sea lanes in the area as strategically important.

The Philippines has accused China of intruding at least six times in Manila-claimed areas in and near the Spratlys since February. Among the most serious was a reported firing by a Chinese navy vessel on Feb. 25 to scare away Filipino fishermen from the Jackson Atoll.

The Philippines, whose poorly equipped forces are no match for China’s powerful military, has resorted to diplomatic protests. President Benigno Aquino III insisted Friday that his country won’t be bullied by China and said Beijing should stop intruding into waters claimed by Manila.

The battle for ownership of the Spratlys has settled into an uneasy standoff since clashes involving China and Vietnam killed more than 70 Vietnamese sailors in 1988.

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Associated Press writer Charles Hutzler in Beijing contributed to this report.