In a flurry of deal-making on the first stop of his Asia trip, Trump oversaw the signing on Sunday of an expanded ceasefire pact between Cambodia and Thailand and four regional trade deals.
None of those framework deals reduced steep US tariffs on Cambodia, Malaysia, Thailand and Vietnam, the White House said, although they left room for some exemptions.
"Our message to the nations of Southeast Asia is that the United States is with you 100 per cent and we intend to be a strong partner for many generations," Trump said on a day when US and Chinese negotiators agreed to a tariff pause in their trade war.
While Trump and Secretary of State Marco Rubio fly to Japan, top officials from China and the leaders of Brazil, Canada, the European Council and the 11-strong ASEAN bloc will work to solidify economic partnerships and hammer out trade pacts.
Chinese officials are expected to press for trade multilateralism and shore up regional relationships, while other US officials attend the summit after Rubio's departure.
Also on the cards is a summit of the China-backed Regional Comprehensive Economic Partnership, which groups 10 ASEAN members with Australia, Japan, New Zealand and South Korea.
The world's largest trading bloc, the partnership covers about 30 per cent of global gross domestic product and is touted by some analysts as a potential buffer against US tariffs.
European Council President Antonio Costa met Chinese Premier Li Qiang and said he conveyed strong concern about Beijing's expansion of export controls on critical raw materials.
"I urged him to restore as soon as possible fluid, reliable and predictable supply chains," Costa said after the meeting, adding that he had also sought China's help in efforts to end Russia's war in Ukraine.
Rare earth magnets and minerals have been a major sticking point in Beijing's trade war with Washington, with China using its control over 90 per cent of the global supply as leverage to combat US tariffs.
Brazilian President Luiz Inacio Lula da Silva said his meeting with Trump on Sunday "guaranteed" a more favourable trade deal.
The US has imposed tariffs of 50 per cent on Brazilian products in retaliation for the sentencing of former President Jair Bolsonaro.
"I told him it was extremely important to take into account Brazil's experience as the largest country in South America, as the most economically important country that has almost all of South America as a neighbour," Lula, as he is popularly known, said on Monday.
The Association of Southeast Asian Nations (ASEAN) groups Brunei, Cambodia, Indonesia, Laos, Malaysia, Myanmar, the Philippines, Singapore, Thailand, East Timor and Vietnam.
