Coastguard officials said they have struggled to cope since the oil tanker Solar I sank last Friday with more than 520,000 gallons of industrial fuel on board.
The tanker went down in rough seas in the Panay Gulf between the central islands of Panay and Guimaras. Eighteen crew members were rescued but two remain missing, the coastguard said.
Lieutenant-Commander Joseph Coyme, a coastguard spokesmanon, said on Wednesday: "We don't have the capability right now to salvage sunken vessels this deep. That's why we're seeking international support."
The leaking tanker is resting on the seabed in around 900m (3,000ft) of water.
Other coastguard officials said that the government wanted to hire foreign salvage crews to refloat the tanker as well as specialist vessels to contain the slick, which is about 460km (280 miles) south of Manila.
Coyme also said they hoped to contain the 19.5 nautical mile long slick off the southern coast of Guimaras.
Local salvage crews have attempted to put floating booms around the spill to stop it spreading, but their work has been hampered by rough seas.
Joaquin Carlos Nava, the governor of Guimaras province, said the slick had reached more than 200km of coastline and damaged mangrove swamps, seaweed plantations and coral reefs containing popular dive sites.
Houses on the Guimaras's coast
are smeared with bunker oil
Nava said that in his province alone up to 10,000 fishermen and their families were being affected.
"It is not only the coastline and fishing industries that are affected, but also the tourism industry. We are looking at the possible evacuation and support for our displaced fisherfolk. We don't know how long this [cleanup] will take," he said.
"I don't think we can do this alone. All we can do is try to mitigate the impact of the spill on our shoreline," he said.