President Donald Trump has said the US will no longer tolerate "chronic trade abuses", in a defiant address at the Asia-Pacific Economic Co-operation (Apec) summit in Vietnam.
He said the US was prepared to work with Apec countries as long as they "abide by fair reciprocal trade".
Mr Trump said free trade had cost millions of American jobs, and he wanted to redress the imbalance.
He has already visited China and Japan as part of a five-nation Asia tour.
Apec brings together 21 economies from the Pacific region - the equivalent of about 60 per cent of the world's GDP.
Since taking office, President Trump has pulled the US out of the Trans-Pacific Partnership, a major trade deal with 12 Apec member countries, arguing it would hurt US economic interests.
Chinese President Xi Jinping also addressed the summit in the Vietnamese port city of Da Nang, where he said that globalisation was an irreversible trend but the world needed to make it more balanced and inclusive.
What did Trump say?
In his speech on Friday, President Trump railed against the World Trade Organization, which sets global trade laws, and said it "cannot function properly" if all members do not respect the rules.
He complained about trade imbalances, saying the US had lowered market barriers and ended tariffs while other countries had not reciprocated. "Such practices hurt many people in our country," he told business and political leaders at the summit.
But he did not lay the blame on Apec countries, and instead accused earlier US administrations of not acting earlier to reverse the trend.
He said America would make bilateral agreements with "any Indo-Pacific partner here who abides by fair reciprocal trade", but only "on a basis of mutual respect and mutual benefit".
Mr Trump has repeatedly referred to the region as "Indo-Pacific", a term used to define America's new geopolitical view of Asia.
"Indo-Pacific" - Trump's latest catchphrase
The US president had travelled to Da Nang from Beijing, where he had also discussed America's huge trade imbalance with China. There too, he said he did not blame the country for "taking advantage".
America's narrowing role in Asia-Pacific
By Jonathan Head, BBC South East Asia correspondent
This was a strong, confident speech by President Trump giving two starkly contrasting messages. He opened with glowing praise for the achievements of the Asia Pacific region. He listed most of the larger members of APEC, his flattery bringing applause from the audience, none louder than that which greeted his description of Vietnam's 2000-year struggle for statehood. He brushed over the Vietnam War.
Then came a list of America's grievances on trade. His reference to currency manipulation, and forcing companies to give up their intellectual property to get market access were clearly directed at China. Instead of multilateral arrangements, he offered new, bilateral agreements with countries prepared to give America a better deal.
Mr Trump made no mention of the leadership the US has traditionally offered, in values, economic philosophy and military alliances. There was no mistaking the narrower role he sees for the US in the Asia Pacific region.
Balancing trade and language
The total trade relationship between the US and China was worth $648bn last year, but trade was heavily skewed in China's favour with the US amassing a nearly $310bn deficit.
Mr Trump has in the past accused China of stealing American jobs and threatened to label it a currency manipulator, though he has since rowed back on such rhetoric.
China said on Thursday it would further lower entry barriers in the banking, insurance, and finance sectors, and gradually reduce vehicle tariffs.
Mr Xi promised "healthy" and "balanced" economic and trade relations.
Deals worth $250bn (£190bn) were also announced, although it was unclear how much of that figure included past agreements or potential future deals. At the same time, US Secretary of State Rex Tillerson told journalists the deals were "pretty small" in terms of tackling the trade imbalance.
Before the Beijing talks, Mr Trump in Tokyo lashed out at Japan, saying it "has been winning" on trade in recent decades.
Japanese Prime Minister Shinzo Abe will also be making a speech at the Apec summit. Japan had a $69bn (£52.8bn) trade surplus with the US in 2016, according to the US Treasury department.
After attending the Apec summit, Mr Trump will pay a state visit to the Vietnamese capital Hanoi.
Mr Trump will end his 12-day Asian tour in the Philippines on 13 November.
