Joe Biden says the United States needs to negotiate with allies to set global trading rules to counter China's growing influence.
However the president-elect has declined to say whether he would join a new China-backed Asian trade pact signed on Sunday.
Asked in Delaware whether the United States would join the Asian-focused 15-country Regional Comprehensive Economic Partnership agreement, Biden said he could not yet discuss US trade policy because he had not taken office "and there's only one president at a time".
"We make up 25 per cent ... of the economy in the world," Biden said of the United States.
"We need to be aligned with the other democracies, another 25 per cent or more so that we can set the rules of the road instead of having China and others dictate outcomes because they are the only game in town."
The signing of the RCEP at a regional summit in Hanoi creates the world's largest trade agreement, covering 30 per cent of the global economy and 30 per cent of the global population, joining for the first time Asian powers China, Japan and South Korea.
It also marks a another setback for US influence in the region after President Donald Trump in 2017 quit the 12-country Trans-Pacific Partnership trade pact, negotiated while Biden was vice president.
Biden said he had a detailed trade plan he would discuss on January 21, 2021, the day after he is due to be sworn into office.
While TPP members including Japan and many free-trade advocates have expressed hope Biden will rejoin that trade pact, he has said little about it and advisers have said he would not immediately remove tariffs on Chinese goods.
Biden said he had told leaders the United States would approach trade by insisting Washington would "invest in American workers and make them more competitive", make sure that labour and environmental interests were represented in any new trade negotiations and stop "poking our finger in the eyes of our friends".
Asked why he would not comment on trade agreements when he has said he would rejoin the World Health Organization and Paris Climate Accords, Biden said: "You're asking me about whether I'd join a specific proposal, the details of which are now only being negotiated among those nations.
"It would require a negotiation."