The Philippines and Vietnam have agreed to draft a six-year action plan to deepen their security ties in the face of China's growing assertiveness in the disputed South China Sea.

In a statement yesterday, Philippine Foreign Minister Jose Rene Almendras said in Hanoi that the 2017-2022 plan would cover defence and security as well as terrorism and transnational crimes.

The Philippines and Vietnam signed a strategic partnership agreement on the sidelines of the Apec Economic Leaders' meeting in November last year.

Philippine President Benigno Aquino said at the time that he expected the partnership to lead to "increased collaboration between our respective defence agencies".

The Philippines and Vietnam - former Cold War adversaries - both have competing claims with China over the South China Sea. Other claimants to the sea include Malaysia, Brunei and Taiwan.

In exchanges with his Vietnamese counterpart Pham Binh Minh during his visit, Mr Almendras said "emphasis was given on the vital role that Asean centrality and solidarity play, including the non-claimant states, in coming up with a common position regarding the issue of the (South China Sea)".

In Manila, meanwhile, Philippine Ambassador to the United States Jose Cuisia warned yesterday that disputes in the region could escalate further if China moves to turn Scarborough Shoal, in the northern half of the South China Sea, into an island.

Mr Cuisia said the US should convince China not to take this "very provocative" step.

Admiral John Richardson, the head of US naval operations, reported last month spotting a suspected Chinese survey ship in Scarborough. The chain of reefs and rocky outcrops surrounding a lagoon lies just 198km west of the Philippines.

China roped off Scarborough, which it refers to as Huangyan Island, in 2012, when it figured in a tense, two-month stand-off with the Philippines.