US President Donald Trump's blitz of tariffs and trade war with China has shaken the export-dependent Asia-Pacific region, and his trade representative, Jamieson Greer, is set to attend the summit and hold bilateral talks with attendees.

- What is APEC? -

The 21-member APEC group includes Australia, Indonesia, Vietnam, China, Russia, Japan, the United States, Canada, Mexico and Chile.

Established in 1989, it aims to promote regional integration and economic cooperation.

APEC members account for around 37 percent of the global population, 60 percent of the world's GDP and nearly half of global trade.

But it has been unable to exert meaningful political influence in the face of Trump's tariffs, which have hit Asian economies hard.

"APEC has always struggled to show relevance," said Deborah Elms, a trade analyst at the Hinrich Foundation, describing the group as an incubator for "non-binding ideas".

While the ideas exchanged at APEC meetings may not appear in official commitments, they "can form the basis of discussions, negotiations, and commitments in other settings", she told AFP.

- Does it matter? -

Experts say that now is the moment for the group to prove its worth, as trade tensions escalate along with increasing tariff disputes.

"The APEC has never been more important," said Christopher Findlay, an honorary public policy professor at the Australian National University.

In the face of Trump's tariffs, "APEC's role in articulating the continuing relevance of economic integration -- and how to get there -- is more important than ever," he added.

- What's happening to regional trade? -

Asian nations are "increasingly tied to China, both from a final demand perspective and via integrated supply chains", even as companies relocate to countries like Vietnam to avoid US tariffs, Katrina Ell, an economist at Moody's Analytics, told AFP.

Yet the "US still remains a critical and large final destination for goods... making (Asian countries) vulnerable to the chaotic US trade policy because it relies on demand from the US consumer," she said.

Despite their varied economic strengths and development levels, experts say that APEC members share a common interest in defending free trade.

- What can Jeju offer? -

The Jeju meeting gives APEC countries a chance to "refine its cooperative options for responding (to the United States) and identify new opportunities for deepening their own integration", Findlay said.

"The US's protectionist stance has been an important stimulant for bilateral and multilateral negotiations outside of the US," added Ell.

"Economies outside of the US have been scrambling to cement closer ties with each other, recognising that the benefits of free trade have not been forgotten."

However, she warned that Asian consumption, even if growing, "cannot completely replace US demand".

- What about the United States? -

It is one of US Trade Representative Greer's first international trips since taking office, and the Jeju meeting is likely to be "a critical platform for tariff negotiations beyond APEC", said South Korea's vice minister of industry, Park Sung-taek, in late April.

Kim Dae-jong, a professor at Sejong University, told AFP that "numerous negotiations could take place", particularly between South Korean and US officials.

The United States itself "may recognise the importance of expanding trade for the global economy", Kim said.

Elms, the analyst, added that amid the trade war, APEC's role in organising bilateral meetings between member countries cannot be overlooked.

- Will there be trade deals? -

Even a series of bilateral tariff talks between the United States and its partners would be significant, experts say.

But agreements on broader cooperation within APEC may be hindered not just by Trump's trade war, but by other ongoing tensions between the United States and China, as well as Russia.

"I don't think the meeting will produce a clear outcome," warned Kim Yong-jin, a professor at Sogang University.

It is more likely to result in "in a general message of cooperation" without substantive deals.

Even agreeing on the rules of the game would be a step forward.

"The important thing is for ministers to agree on a rational approach," said Kim. "But the United States seems focused solely on the trade deficit."