In late March, the Philippines announced the deployment of additional naval ships to the disputed South China Sea after the nation's Coast Guard reported that about 200 vessels believed to be part of the Chinese state-funded maritime militia were seen attached in a line formation in the Whitsun Reef. The Philippines also filed a diplomatic protest over the issue and demanded these vessels leave the area. Beijing, in turn, denied that the boats belonged to the maritime militia.
"National Security Adviser Jake Sullivan spoke by phone today with National Security Adviser Hermogenes Esperon of the Philippines. The National Security Advisers discussed their shared concerns regarding the recent massing of People's Armed Forces Maritime Militia vessels at Whitsun Reef", the White House said in a statement.
The US official also reaffirmed that Washington considered the US-Philippines Mutual Defence Treaty applicable in the South China Sea, the White House added.
"The National Security Advisers agreed that the United States and the Philippines will continue to coordinate closely in responding to challenges in the South China Sea", the statement said.
The Whitsun Reef belongs to the Spratly archipelago, which is claimed by Brunei, China, Malaysia, the Philippines, Taiwan, and Vietnam. China considers the Spratly archipelago to be its territory, despite a Hague-based Permanent Court of Arbitration ruling, saying there was no legal basis for China's maritime claims. The arbitration proceeding was initiated by the Philippines in January 2013.