INTERNATIONAL NEWS - 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% 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.
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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.
