Defence Secretary Delfin Lorenzana made the comments four days after US Secretary Mike Pompeo said Washington would intervene in case of an armed attack on Philippine forces or vessels in the disputed South China Sea.

"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," Lorenzana said in a statement.

Filipino officials have suggested the Philippines' 1951 mutual defence treaty with the US may not apply in the strategic waterway, since Washington has not stopped Beijing building artificial islands over reefs claimed by Manila and other neighbours.

The US has said it does not take sides in the dispute over the South China Sea claimed by Beijing as well as the Philippines, Brunei, Malaysia, Taiwan and Vietnam. It has however sailed warships near the Chinese-built islands to assert free passage.

Pompeo said Friday China's actions in the waterway -- through which trillions of dollars of global trade passes each year -- threaten both the US and the Philippines, and vowed to keep it open.

But Lorenzana said the naval manoeuvres risked dragging the Philippines into armed conflict.

"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," he said, referring to Filipino-claimed areas of the sea.

"In such a case and on the basis of the (treaty), the Philippines will be automatically involved," he said.

The "vastly different" security environment now in place "necessitates a review of the treaty", he added.