The Philippines wants to ensure US warships are closer to the disputed South China Sea by offering the US a naval base on a western island.

The Philippines wants to ensure US warships are closer to the disputed South China Sea by offering the US a naval base on a western island, Reuters reported.

China has stepped up its activities to assert its extensive claim over the energy-rich South China Sea.

Brunei, Malaysia, the Philippines, Vietnam and Taiwan also have claims over the sea, or parts of it, through which about $5 trillion of ship-borne goods pass every year.

Last month, the Philippines and the United States signed an Enhanced Defense Cooperation Agreement (EDCA) allowing U.S. forces wider access to Philippine bases and building facilities for joint use in maritime security and disaster response.

"Oyster Bay is still underdeveloped but we need to improve it for our armed forces," armed forces chief of staff General Emmanuel Bautista said in a television interview late on Wednesday, referring to a base on Palawan island to the west of main Philippine islands.

"Perhaps with the EDCA that can be facilitated and further improvement in Oyster Bay will be made."

Bautista said he was hoping the U.S. would help pay for the development of the base, where the Philippines has begun work, and help develop it into a major operating base for both navies.

Oyster Bay is only 160 km (100 miles) from the disputed Spratly islands, where China has been reclaiming a reef known as Johnson South Reef, and building what appears to be an airstrip on it.

The Philippine foreign ministry released on Thursday aerial surveillance photographs of the reef showing some work had been done.

In October, the Philippine navy commander on Palawan told Reuters the force had a plan to convert Oyster Bay into a "mini-Subic" where the country's two former U.S. Coast Guard cutters would be based.

Subic Bay is a former U.S. naval base which is now a commercial free port, where U.S. warships dock because of its deep harbor. There are plans to convert parts of the free port into an air and naval base.

Bautista said the Philippines was also offering the United States the use of a base in the Zambales area and an army jungle training base in Fort Magsaysay in the Nueva Ecija area.