ASEAN gathers in shadow of US-China trade war

"ASEAN has great potential, but fully realizing it depends on whether we choose to become more integrated, and work resolutely towards this goal in a world where multilateralism is fraying under political pressures," Lee said.

Chinese Premier Li Keqiang and US Vice President Mike Pence are expected at the meetings this week, along with Russian President Vladimir Putin, Indian Prime Minister Narendra Modi and Japanese Prime Minister Shinzo Abe.

US President Donald Trump, who pulled the US out of the Trans-Pacific Partnership (TPP) trade deal and initiated a trade spat with China, will not be attending the summit after doing so last year. Trump and Chinese President Xi Jinping are set to hold talks at the end of the month in a widely anticipated meeting in Buenos Aires in a bid to tamp down tit-for-tat trade retaliation.

The Association of Southeast Asian Nations (ASEAN) celebrated its 50th anniversary last year. Since its founding, the bloc has emerged as a beacon of unity in Southeast Asia, although it has often struggled to find consensus among members over key policy issues affecting the region's politics, security and the economy, among other things.

The US-China trade row has the potential to harm markets beyond the world's two largest economies, including the ASEAN members, and leaders gathered in Singapore are expected to express their concerns to Pence and Li.

Many of the countries attending the ASEAN summit are expected to announce progress on the Regional Comprehensive Economic Partnership (RCEP) pact currently under negotiation.

The pact is less robust than TTP and groups the 10 ASEAN members plus China, India, Japan, South Korea, Australia and New Zealand.