By Karen Lema
(Reuters) - Philippine President Ferdinand Marcos Jr has said the prospect of tensions escalating over Taiwan was a "grave concern" to Southeast Asian leaders and discussions about it were inevitable at this week's summit in Indonesia.
"Considering that we agree on the concept of ASEAN centrality when it comes to regional concerns, that will be one of the most important subjects that we will bring up," Marcos told reporters late on Tuesday.
Marcos was in Indonesia for the Association of Southeast Asian Nations (ASEAN) summit, where he will seek the completion of a code of conduct for the South China Sea.
"I will bring it up again," Marcos said. "The issues ... they will not calm down until we have a code of conduct."
The Philippines, which won an arbitration case in 2016 that clarified its sovereign rights and invalidated China's claim of historic jurisdiction over the entire South China Sea, has complained of late about Beijing's "dangerous manoeuvres" and "aggressive tactics".
China says it is operating lawfully in its territory.
Marcos was in the United States last week and met counterpart Joe Biden, after which he secured a clear-cut treaty commitment from Washington that it would defend the Philippines if attacked in the South China Sea.
ASEAN and China have been working towards a maritime code of conduct following a commitment they made in 2001, a set of rules that many analysts expect will, if they materialise, be non-binding and have no enforcement mechanism.
China's claims run more than 1,500 km (932 miles) off its coast and into the exclusive economic zones of five ASEAN countries - Brunei, Malaysia, the Philippines, Vietnam and Indonesia - where Beijing's coast guard and armada of fishing vessels have been accused of using intimidation tactics.
Marcos said he hoped the code of conduct would be in place "sooner rather than later because the tensions are increasing."
(Reporting by Karen Lema in Manila; Editing by Martin Petty)