MANILA, Philippines — The United States has vowed to support long-time ally the Philippines in case of any armed attack in the South China Sea, part of which is the West Philippine Sea, as part of a treaty between the two countries.

In his visit to Manila, US Secretary of State Mike Pompeo pointed out that Beijing's military activities in the South China Sea threaten the country's sovereignty, security and economic livelihood.

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"As the South China Sea is part of the Pacific, any armed attack on Philippine forces, aircraft or public vessels in the South China Sea would trigger mutual defense obligations under Article 4 of our Mutual Defense Treaty," Pompeo said in a press conference Friday.

Article of the 1951 MDT between the Philippines and the US indicates that:

"Each Party recognizes that an armed attack in the Pacific area on either of the Parties would be dangerous to its own peace and safety and declares that it would act to meet the common dangers in accordance with its constitutional processes.

Any such armed attack and all measures taken as a result thereof shall be immediately reported to the Security Council of the United Nations, Such measures shall be terminated when the Security Council has taken the measures necessary to restore and maintain international peace and security."

The American top envoy said he discussed this with President Rodrigo Duterte and Foreign Affairs Secretary Teddy Locsin Jr. during their meeting Thursday night.

Pompeo stressed that the disputed South China Sea is an important body of water for freedom of navigation.

"We remain committed to supporting not only the Philippines in that effort and the Philippines will need to do its part as well but all the countries in the region so that these incredibly vital economic sea lanes are open and China does not pose a threat to closing them down," Pompeo said.

The Trump administration has made it clear that it is committed to ensuring that the South China Sea remains open to all countries, as well as for commercial transit.

For Locsin, a review of the defense treaty between Manila and Washington is not necessary.

"My own view is no. I believe in the old theory of deterrence," Locsin told reporters.

The Philippines' top diplomat expressed confidence that the US is committed to its obligations on the country.

Defense Secretary Delfin Lorenzana earlier suggested reviewing the provisions of the MDT given the maritime dispute in the South China Sea.

US Ambassador to the Philippines Sung Kim had welcomed this proposal, saying that the agreement should be looked into to see "whether we can make any adjustments to make even better what it is now."