MANILA- (UPDATE) The Philippines is mulling a review of its decades-old mutual defense treaty with the United States and how it applies to the situation in the West Philippines Sea.

Defense Chief Delfin Lorenzana said Thursday the government is studying ways for the Philippines to get a better deal under the treaty.

"We'll look into that, review. We have to look into the provisions, discuss, with the end of review it to make it stronger or whatever to improve our alliance with the United States," he told reporters.

The United States and the Philippines are already long-time allies bound by a mutual defense pact, and engage in regular war games that see thousands of US troops and state-of-the-art American military hardware brought to Manila.

Under the treaty, Manila and Washington are bound to aid each other in the event of an attack. However, the treaty's role in the Philippines' sea dispute with China remains unclear.

• Does PH-U.S. Mutual Defense Treaty cover the South China Sea?

Lorenzana said it is the US interpretation that the treaty covers only "metropolitan" Philippines, noting that this does not include the Philippine-occupied areas in the West Philippine Sea.

“Ang sinasabi nila sa Mutual Defense Treaty natin is Metropolitan Philippines lang and I think their definition of Metropolitan Philippines is just the whole country, plus yung mga island natin na sakop natin," he told reporters.

(The Mutual Defense Treaty only covers Metropolitan Philippines and I think their definition of Metropolitan Philippines is just the whole country, plus the islands we cover.)

Filipino troops are currently occupying 9 areas in the South China, and the largest, Pag-asa Island, serves as the seat of government of Kalayaan town in Palawan. Soldiers began occupying these areas in 1968, or 17 years after the defense pact was forged.

Lorenzana said the Americans are "ambivalent" when it comes to the issue on whether the Philippine-occupied areas in the South China Sea are included in the "metropolitan" Philippines.

"I think their definition of metropolitan Philippines is just the whole country...I think Kalayaan is not included...Thats our problem because US has always said that they will not meddle into territorial disputes," he said.

The Philippines has long been at odds with China over several features in the West Philippine Sea that Bejing claims ownership of.

Ties however have substantially warmed under the leadership of President Rodrigo Duterte who refused to assert Manila's claims in the disputed waters in exchange for investment opportunities with Asia's largest economy.

• Defense pact can be invoked if US recognizes Panatag as PH territory: analyst

-report from Jorge Cariño, ABS-CBN News