China will boost purchases of US goods and services by $US200 billion ($A290 billion) over two years in exchange for the rolling back of some tariffs under an initial trade deal signed by the world's two largest economies.
The pact defuses an 18-month row that has hit global growth.
Key world stock market indexes climbed to record highs after the deal was signed on Wednesday in Washington, but later stalled on concerns it may not ease trade tensions for long, with numerous thorny issues still unresolved.
President Donald Trump hailed the agreement as a win for the US economy and his administration's trade policies.
"Together, we are righting the wrongs of the past and delivering a future of economic justice and security for American workers, farmers and families," Trump said at the White House alongside US and Chinese officials on Wednesday.
Chinese Vice Premier Liu He read a letter from President Xi Jinping in which the Chinese leader praised the deal as a sign the two countries could resolve their differences with dialogue.
The centrepiece of the deal is a pledge by China to purchase at least an additional $US200 billion worth of US farm products and other goods and services over two years, above a baseline of $US186 billion in purchases in 2017, the White House said.
Commitments include $US54 billion in additional energy purchases, $US78 billion in additional manufacturing purchases, $US32 billion more in farm products, and $US38 billion in services, according to deal documents released by the White House and China's Finance Ministry.
Liu said Chinese companies would buy $US40 billion in US agricultural products annually over the next two years "based on market conditions" which may dictate timing of purchases in any given year.
Beijing had baulked at committing to buy set amounts of US farm goods earlier, and has inked new soybean contracts with Brazil since the trade war started.
Liu later said the deal would not affect "third parties' interests", apparently in reference to deals made with other suppliers of farm goods.
Chinese companies will import US agricultural goods according to consumers' need, and demand and supply in the market, Liu told reporters, according to CCTV.
Although the deal could be a boost to US farmers, car makers and heavy equipment manufacturers, some analysts question China's ability to replace imports from other trading partners with more shipments from the US.
Trump said China had pledged action to confront the problem of pirated or counterfeited goods and said the deal included strong protection of intellectual property rights.
Washington's insistence on enforcement mechanisms "with real teeth" could tear the deal apart if any tariffs are re-imposed for non-compliance.
US Speaker of the House of Representative Nancy Pelosi said Trump's China strategy had "inflicted deep, long-term damage to American agriculture and rattled our economy in exchange for more of the promises that Beijing has been breaking for years."
The Phase 1 deal cancelled planned US tariffs on Chinese-made mobile phones, toys and laptop computers and halved the tariff rate to 7.5 per cent on about $US120 billion worth of other Chinese goods, including flat-panel televisions, Bluetooth headphones and footwear.
But it will leave in place 25 per cent tariffs on a $US250-billion array of Chinese industrial goods and components used by US manufacturers, and China's retaliatory tariffs on over $US100 billion in US goods.
Trump, who has been touting the Phase 1 deal as a pillar of his 2020 re-election campaign, said he would agree to remove the remaining tariffs once the two sides had negotiated a "Phase 2" agreement.