By Karen Lema and Poppy McPherson

BASA AIR BASE, Philippines (Reuters) - The United States and Philippines will announce new sites as soon as possible for an expanded Enhanced Defense Cooperation Agreement (EDCA), which gives the Western power access to military bases in the Southeast Asian country.

Philippine President Ferdinand Marcos Jr last month granted the United States access to four military bases, on top of five existing locations under the 2014 EDCA, which comes amid China's increasing assertiveness towards the South China Sea and self-ruled Taiwan.

Speaking at the Basa Air Base in Manila, one of the existing EDCA sites, visiting U.S. Air Force Secretary Frank Kendall said the defence agreements between the two countries were "not focused on any particular issue."

EDCA allows U.S. access to Philippine bases for joint training, pre-positioning of equipment and building of facilities such as runways, fuel storage and military housing, but it is not a permanent presence.

While the Philippines has yet to formally identify the sites, a former military chief has publicly said the United States had asked for access to bases in Isabela, Zambales and Cagayan, all on the island of Luzon, facing north towards Taiwan, and on Palawan in the southwest, near the disputed Spratly Islands in the South China Sea.

Leaders of local governments at the potential EDCA sites have backed the government's decision to allow the United States greater access to the bases, Philippines' defence chief, Carlito Galvez, said in a joint news conference with Kendall.

Galvez and Kendall were leading a groundbreaking ceremony for the rehabilitation of the Basa Air Base's runway.

"Today's event is a physical manifestation of our Enhanced Defense Cooperation Agreement, a key pillar of the U.S.-Philippine alliance," Kendall said in a speech, adding it built on a seven-decade-old Mutual Defense Treaty that applied anywhere in the South China Sea.

"We are at an inflection point in history and our cooperation will help ensure we stay on the path to peace and stability," he added.

The runway rehabilitation is part of $82 million the United States has allocated for infrastructure investments at the existing five EDCA sites.

"Moving forward we hope the U.S will consider more EDCA projects," Galvez said.

(Reporting by Karen Lema, Poppy McPherson; Editing by Kanupriya Kapoor, Martin Petty)