Beijing (AFP) - Trade tensions between the world's two biggest economies rose again on Tuesday as Beijing accused Washington of "excessive protectionism" after targeting imports of a key chemical from the United States.
The administration of US President Donald Trump has brought a range of commerce cases against China, sparking fears of a trade war.
"China is concerned about the US's serious trend towards trade protectionism in steel products," the Ministry of Commerce said in a statement, and "calls on the US to restrain itself from using trade restriction measures".
More than half of the US's protective tariffs are related to steel, it noted.
A director of the ministry's trade remedy and investigation bureau Wang Hejun was quoted as saying that "repeated and excessive protectionism" often "brings about a vicious circle".
The statement followed news late Monday that Beijing had taken aim at imports of a key chemical from the United States.
The commerce ministry said it had found dumping of styrene imports from the US, Taiwan and South Korea, in an initial ruling during a continuing trade investigation into the chemical.
Dumping, or selling goods at unfairly low prices abroad, can undercut domestic markets at the expense of local industries.
"Mainland China's styrene industry has suffered substantial harm," the ministry said in a statement, adding that dumping was the cause of this.
The initial ruling called for importers to place anti-dumping deposits of five to 10.7 percent with China's customs administration.
Those deposits will be applied to tariffs if the ministry decides in a final ruling to levy such duties.
Styrene is the building block of many plastics. It is used to make foam packaging and many disposable plastics.
Last year China imported 3.2 million tonnes of the chemical worth more than $4 billion from the US.
The measures come a month after the Trump administration slapped new tariffs on Chinese-made solar panels and washing machines.
Those tariffs followed a series of trade cases brought against China during Trump's first year in office, which have rattled Beijing.
More are expected soon. The Trump administration has major decisions looming on Chinese aluminium, steel and intellectual property practices.
Analysts say Beijing is signalling it will take action in any tit-for-tat trade war.
Last week it launched an anti-dumping investigation into sorghum imports from the US, worth almost $1 billion last year.
That was a sliver of the $14 billion in US soybean imports, which a Chinese commerce ministry spokesman last week hinted could also be in Beijing's crosshairs.
Soybeans are America's largest export to China.
Washington says achieving a level playing field in trade is near the top of its agenda in Sino-US relations.
But in Trump's first year as president the trade deficit swelled to a record high of $375.2 billion by the US's counting.