The US and China have exchanged the first salvos in what could become a protracted trade war, slapping tariffs on $US34 billion worth of each other's goods and giving no sign of willingness to discuss a truce.
Duties on a range of Chinese goods imported into the US took effect on Friday and were immediately countered by measures from China, with Beijing accusing the US of triggering the "largest-scale trade war".
The escalating fight between the world's two biggest economies means it could "take economic and political pain to get these two parties to the (negotiating) table", says Scott Kennedy, head of China studies at the Center for Strategic and International Studies in Washington.
President Donald Trump is already threatening additional rounds of tariffs, possibly targeting more than $US500 billion ($A673 billion) worth of Chinese goods, about the total amount of US imports from China last year.
Erin Ennis, senior vice-president of the US China Business Council, said there was a danger the two sides will dig in on trade sanctions without a clear strategy for resuming negotiations.
While US companies doing business in China agree with Trump's complaint about Chinese intellectual property practices, Ennis said they did not see tariffs pushing China into submission.
China's commerce ministry said it was forced to retaliate, meaning imported US goods including cars, soybeans and lobsters also faced 25 per cent tariffs.
Some of Trump's fellow Republicans in Congress lashed out at his actions.
"Tariffs not only hurt our farmers, ranchers and aeroplane manufacturers but they also harm every American consumer. We should be working with our allies to isolate China rather than escalate a trade war," said Senator Jerry Moran, who represents the agriculture-heavy state of Kansas.
Friday's China tariff volley fuelled fears a prolonged battle would hurt global trade, investment and growth.
"Trade war is never a solution," Chinese Premier Li Keqiang said at a news briefing with Bulgarian Prime Minister Boyko Borissov in Sofia before a summit with 16 central and eastern European countries.
"China would never start a trade war but if any party resorts to an increase of tariffs then China will take measures in response to protect development interests."
There was no sign of renewed negotiations between US and Chinese officials before Friday, business sources in Washington and Beijing said.
The dispute has roiled share, currency and commodity markets in recent weeks.
China lodged a case with the World Trade Organisation against the US, its commerce ministry said on Friday.
White House Council of Economic Advisers chairman Kevin Hassett told the Fox Business Network on Friday that Trump was "going to deliver better (trade) deals".
He said, for now, "he's called the bluff of other countries that have basically been abusing" US companies and workers.
China's tariff list is heavy on agricultural goods such as soybeans, sorghum and cotton, threatening US farmers in states that backed Trump in the 2016 US election, such as Texas and Iowa.