The 80-year-old vessel, however, would not quite make its own funeral.

Onlookers instead watched as the ship, which once chased Japanese submarines and ferried German prisoners as part of the US fleet, sank before the first volley could be fired.

"The Balikatan 25 maritime strike targets vessel sank off the west coast of the Philippines prior to the event commencing today," Philippine Navy spokesman John Percie Alcos said in cancelling a planned media event.

"Due to rough sea conditions ... and with its long service life... she took on a significant amount of water and eventually sank," he said

Praising it as one of the most-decorated ships in Philippine history, Alcos added the country was proud to be "transitioning to a new and multi-capable navy".

After more than 20 years of service, the vessel -- then named USS Brattleboro -- was sold to the Republic of Vietnam in 1966.

The Philippine Navy acquired and refurbished the ship after its crew fled Vietnam following the 1975 fall of Saigon.

Balikatan, three weeks of US-Philippine joint exercises aimed at deterring Beijing's ambitions in the disputed South China Sea, is set to end Friday.