A South China Sea confrontation this week, in which the Chinese coast guard personnel brandished weapons and rammed Philippine naval vessels, does not trigger Manila's mutual defence pact with the United States, a spokesperson for President Ferdinand Marcos said Friday.

"We are not yet ready to consider this as an armed attack," executive secretary Lucas Bersamin told reporters when asked if Manila would ask Washington to honour the 1951 treaty.

The pact requires both parties to come to the other's defence in case of an "armed attack" against vessels, aircraft, military and coast guard anywhere in the Pacific theatre, which Washington says includes the South China Sea.

Monday's clash saw Chinese coast guard sailors brandishing knives, an axe and other weapons as they stopped a Philippine navy attempt to resupply a Filipino garrison on a derelict warship, seizing guns and damaging other equipment.

A Filipino sailor lost a thumb in the clash, in which the Chinese coast guard confiscated or destroyed Philippine equipment including guns, according to the Philippine military.

Beijing insisted its coast guard behaved in a "professional and restrained" way and blamed Manila for the confrontation, alleging the Philipines had been trying "to sneak in building materials, but also tried to smuggle in military equipment".

The clash was the latest in a series of escalating confrontations as Beijing steps up efforts to push its claims to the disputed area.

The Sierra Madre warship was deliberately grounded atop Second Thomas Shoal in 1999 to assert Manila's territorial claims.

Bersamin downplayed the incident, insisting it was "probably a misunderstanding" and that the Chinese side had not used anything "beyond" bladed weapons.

He said government's advisory National Maritime Council had convened after the confrontation on the president's orders, and recommended that Manila publish the schedule of its resupply missions to the Sierra Madre in advance in hopes China would act in a more restrained manner.

Manila would not be "giving up anything" by adopting that stance, he said, while stressing Marcos has yet to approve the proposal.