Energy Secretary Alfonso Cusi defended on Friday the Philippines' signing of a memorandum of understanding with China on oil and gas development, which may take place at the disputed South China Sea.

In a statement, the Department of Energy (DOE) chief said it is his priority to "safeguarding our country's long-term energy security."

"A component of this is developing new indigenous energy resources in the West Philippine Sea," he said.

The Philippines calls the area within its 200 nautical miles exclusive economic zone in the South China Sea as West Philippine Sea.

The MOU between the Philippines and China about cooperation on oil and gas development was one of the 29 deals that the two countries inked during the state visit of Chinese President Xi Jinping in the country early this week.

There were calls for the government to disclose the deal.

But Cusi said, "I would ask for everyone's patience until the full details are ready to be made public."

He said the MOU signed with China provides a framework for any possible future cooperation, "which may or may not include joint exploration between the Philippines and China in the West Philippine Sea."

But he assured that whatever would be the outcome of the MOU, the rights of existing service contract holders would be protected.

There are areas in the West Philippine Sea which are covered by service contracts. But the contracts have been suspended due to the ongoing territorial disputes between the Philippines and China.

Beijing has been claiming almost the entire South China Sea, including those within the 200 EEZ of the Philippines. This was despite the United Nations Arbitral Tribunal ruling favoring the Philippines and invalidating China's historic and sovereign claim in almost the entire South China Sea through its nine-dash line. Celerina Monte/DMS