Beijing has warned Washington that any deals they produce "will not take effect" if President Donald Trump's threatened tariff hike on Chinese goods goes ahead.
The warning was issued one hour after delegations led by US Commerce Secretary Wilbur Ross and China's top economic official, Vice Premier Liu He, wrapped up a meeting on Beijing's pledge to narrow its trade surplus.
Mr Ross said at the opening of the meeting the two sides had discussed specific American exports Chinese might purchase, but neither side disclosed details of the talks.
The White House threw the status of the meeting into doubt on Tuesday by renewing a threat to hike tariffs on $50 billion (£37 billion) of Chinese high-tech goods in response to American complaints Beijing steals or pressures foreign companies to hand over technology.
The meeting went ahead despite that, but Beijing said it reserved the right to retaliate.
The Chinese statement said the two sides "achieved positive and concrete progress" on Sunday.
But it said the process should be "based on the premise" the two sides would "not fight a trade war".
"If the United States introduces trade sanctions including a tariff increase, all the economic and trade achievements negotiated by the two parties will not take effect," said the statement, carried by the official Xinhua News Agency.
President Trump is pressing Beijing to narrow its politically volatile trade surplus with the United States, which reached a record $375.2 billion (£281 billion) last year.
Following a Chinese promise on May 19 to buy more American goods following the latest round of talks, US Treasury Secretary Steven Mnuchin said the dispute was "on hold" and the tariff hike would be postponed.
That truce appeared to end with Tuesday's surprise announcement, which also said the White House will impose curbs on Chinese investment and purchases of US high-tech goods and on visas for Chinese students.
