(CNN) The Philippines' top defense official has questioned a key treaty with the US over fears it could drag the country into war in the South China Sea, a day after an American B-52 bomber performed a flyover of the contested region.

Speaking Tuesday, Defense Secretary Delfin Lorenzana said the Philippines-US Mutual Defense Treaty (MDT) was ambiguous and vague and risked causing "confusion and chaos during a crisis."

"The Philippines is not in a conflict with anyone and will not be at war with anyone in the future. But the United States, with the increased and frequent passage of its naval vessels in the West Philippine Sea, is more likely to be involved in a shooting war. In such a case and on the basis of the MDT, the Philippines will be automatically involved," Lorenzana said, according to CNN Philippines

The West Philippine Sea is the local term for the South China Sea, where US naval vessels have been conducting freedom of navigation exercises , sparking furious denunciations from China, which claims much of the region as its territory and has built up and militarized islands and reefs throughout the sea.

On Monday, a US B-52 bomber flew near contested islands in the sea , according to US Pacific Air Forces, which oversees air operations in the region. This was the first flyover involving a nuclear-capable B-52 since November.

The MDT between the US and the Philippines was signed in 1951, in the early years of the Cold War. It commits both countries to come to the assistance of the other in the event of an "armed attack on the metropolitan territory of either of the parties, or on the island territories under its jurisdiction in the Pacific or on its armed forces, public vessels or aircraft in the Pacific."

In December, Lorenzana ordered a review into whether the treaty was "still valid or still relevant today."

"It's a 67-year-old treaty. Is it still relevant to our national interest? That's what we should look at. Let us look at it dispassionately, without considering about past ties, about future ties -- dispassionately," he said, adding the end goal was "to maintain it, strengthen it, or scrap it."

According to the Council on Foreign Relations , the treaty has long been a source of contention in the Philippines because of its vagueness in how it covers disputed territories, such as islands in the South China Sea that both Manila and Beijing claim as their own.

"Differences in interpretation arise from the fact that the United States does not explicitly state whether Philippine-claimed disputed territory falls under the provisions of the mutual defense treaty," CFR said in a 2016 report. "Some of these territorial claims were made in the 1970s, decades after the treaty was ratified."

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Earlier this month, US Secretary of State Mike Pompeo met with Philippines President Rodrigo Duterte and other top officials, during which he sought to reassure Manila of Washington's commitment to the MDT.

"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 will trigger mutual defense obligations under Article 4 of our Mutual Defense Treaty," Pompeo said.

Speaking alongside him, Philippines Foreign Secretary Teodoro Locsin said the two governments "shared the view that the alliance must be able to ensure the unfailing mutual defense of our two countries."

On Monday however, Lorenzana pointed to what he said was previous US failure to uphold its part of the deal and defend the Philippines' territorial integrity.

Following the closure of the US naval base in Subic Bay, west of Manila, in 1992, Lorenzana said "the Chinese began their aggressive actions in Mischief Reef -- not an armed attack -- but it was aggression just the same. The US did not stop it."

Manila has been in an awkward dance between Beijing and Washington for years. Under the previous government of Benigno Aquino, it won a landmark case against China at an international tribunal, which ruled much of Beijing's territorial claims in the South China Sea were unlawful.

Under Duterte however, Manila has moved closer to Beijing , even as the President continued to voice occasional concerns about China's territorial ambitions. In November, the two countries agreed to cooperate on oil and gas exploration in the sea, which Duterte said Beijing was "already in possession" of.

"It's now in their hands. So why do we have to create frictions (and undertake) strong military activity that will prompt response from China?" the President said.

Similar concerns seemed to be on Lorenzana's mind Monday, when he said, "it is not the lack of reassurance that worries me. It is being involved in a war that we do not seek and do not want."