U.S. Secretary of State Michael Pompeo has assured the Philippines that a defense treaty would apply if its vessels or planes are attacked in the South China Sea, sparking a debate within the Southeast Asian nation over whether it should drop plans to review the 1951 agreement.

"China's island-building and military activities in the South China Sea threaten your sovereignty, security and therefore economic livelihood, as well as that of the U.S.," Pompeo said at briefing Friday with Foreign Secretary Teodoro Locsin in Manila. "As the South China Sea is part of the Pacific, any armed attack on Philippine forces, aircraft or public vessels will trigger mutual defense obligations" under the treaty.

In response, Locsin said there was no need to review the U.S. Philippines Mutual Defense Treaty, adding Pompeo and President Donald Trump assured that "We have your back." Presidential spokesman Salvador Panelo said the statements showed the U.S. was backing Philippine claims to disputed parts of the South China Sea, and said American troops could be deployed in a shooting war.