Thailand's prime minister made an impassioned plea against protectionism on Sunday at a meeting of Southeast Asian leaders where the fallout from the US-China tariff war has dominated talks. 

Trade has topped the agenda at the Bangkok meeting, as tit-for-tat tariffs between China and the US cast a dark cloud over global growth.

Thailand, which is chairing ASEAN this year, rallied against global protectionism and called for urgency in concluding talks on Regional Comprehensive Economic Partnership (RCEP)  - a China-led trade pact, which once inked will be the world's biggest.

The RCEP includes all 10 ASEAN economies, plus India, Japan, South Korea, Australia and New Zealand.

"The winds of protectionism are hurting our multilateral trading system," Thai Prime Minister Prayut Chan-O-Cha said Sunday. "ASEAN must hold our hands tightly in negotiating... on the RCEP, so it is concluded this year. It will help off-set any impact from the ongoing trade conflict."

The trade war between the US and China have sent reverberations across the world, said Philippine President Rodrigo Duterte. 

The leaders also adopted the "Bangkok Declaration" to combat maritime debris, including plastic waste, in one of the most polluted waters in the world.

ASEAN leaders often put out an image of unity during the annual summits.