Several Southeast Asian leaders snubbed a meeting with US officials on Monday after President Donald Trump decided not to attend a regional summit in Bangkok.
Just three leaders from the 10-member Association of Southeast Asian Nations (ASEAN) showed up to the session, along with a host of foreign ministers.
Trump has been accused of turning his back on Asian allies for pulling out of a major trade pact, as fellow superpower China pursues its own deals and investment projects in the region.
Washington did not send top officials to the weekend ASEAN summit, instead dispatching commerce secretary Wilbur Ross and national security advisor Robert O'Brien.
Monday's sparsely attended address from O'Brien stood in contrast to earlier ASEAN meetings, which had all been attended by most heads of state.
"It's not appropriate for ASEAN to send leaders when the US representation is not on parity," one diplomat in Bangkok told AFP.
Another diplomat said: "It's not a boycott, it's just that other leaders have other meetings to attend to."
In lieu of Trump's physical presence, O'Brien read a letter from the president inviting "the leaders of ASEAN to join me in the United States for a special summit" in the first three months of next year.
In attendance were the prime minister of Thailand, which is hosting the summit, along with the leaders of Laos and Vietnam, next year's ASEAN chair.
At other events during the summit, members have rallied against protectionism amid fears of dragging global growth made worse by the US-China trade war.
Trump, who attended the 2017 ASEAN meeting in Singapore -- Vice President Mike Pence went to the one in Manila last year -- could not come this year because he was busy with campaign events back home, a senior White House official said.
China's premier and the leaders of India, South Korea and Japan all made an appearance over the weekend, although none of them were expected at Monday's US-ASEAN meeting.
One of Trump's first moves after assuming office was to withdraw from the Trans-Pacific Partnership (TPP), a massive free-trade pact that was billed to be the world's biggest before Washington pulled the plug.
The US withdrawal "was a very strong symbolic act and the trend is continuing," said analyst Alex Holmes from Capital Economics.
"It's allowing China to advance its influence in the region", he told AFP.
The TPP has since been reborn as a watered-down version without the US, eclipsed by a China-backed agreement that is slated to be the world's biggest when finalised.
The 16-nation Regional Comprehensive Economic Partnership (RCEP) -- which could be signed next year -- includes 30 percent of global GDP and loops in half of the world's population.
It includes all 10 ASEAN states plus China, India, Japan, South Korea, Australia and New Zealand -- notably excluding the US.
The deal has gained new momentum as the US-China trade war rumbles on, with the IMF warning that global growth could slow to its lowest rate in 10 years thanks to the tit-for-tat-trade spat between the world's two biggest economies.
RCEP negotiators on Monday were hammering out final details of the deal, with the aim to sign it in February 2020 according to a draft seen by AFP. An official announcement was expected later Monday.
The 11th-hour talks were being held as the ASEAN bloc and its allies espoused open trade in the region.
"We are once again faced with the high winds of trade protectionism," South Korean leader Moon Jae-in said Monday.
"We need to protect the free-trade order... and bring the global economy back on track."
In a brief departure from global trade woes, Moon met Japanese Prime Minister Shinzo Abe on Monday for their first talks in a year amid tensions over a dispute related to Japan's use of forced labour during World War II.
Ongoing troubles in the South China Sea also dominated the ASEAN summit, with Vietnam hoping for tough language against Beijing over its aggression in the resource-rich waterway.
China is accused of building up military installations in the sea, which it claims most of, and in recent weeks sent a survey to Hanoi-claimed waters.