The news reignited concern that the U.S-Chinese row will worsen, damaging the already weakening global economy and curtailing metals demand.
Benchmark copper on the London Metal Exchange (LME) did not trade in official rings but was bid down 0.3 percent at $6,227 a tonne. Global equities markets fell.
Copper was still up around 1.5 percent this week after touching a two-month high of $6,289.50 on Thursday.
"New concerns about the trade dispute are clearly weighing on prices," said Commerzbank analyst Daniel Briesemann, saying an escalation could send copper back towards January's 1-1/2 year low of $5,725 a tonne.
But he said that, if the two sides reach a deal, copper could rise as high as $6,800 in the second quarter, helped by supply shortfalls.
COPPER STOCKS: On-warrant copper stocks available to the market in LME-registered warehouses have fallen to 87,725 tonnes from about 130,000 tonnes in mid-January and are near decade lows, pointing to an undersupplied market. <MCUSTX-TOTAL>
CODELCO: Chilean state miner Codelco said heavy rains had forced a suspension of operations at its northern copper mines Chuquicamata and Ministro Hales.
Chile's copper commission earlier said Codelco saw a 1.9 percent drop in its output in 2018.
EUROPE ECONOMY: The European Commission and the Bank of England have sharply cut their forecasts for economic growth in the euro zone and Britain.
DOLLAR: The US dollar was at two-week highs, further pressuring metals by making them more expensive for buyers holding other currencies.
ZINC SPREAD: Cash zinc has moved from a premium to a discount against the three-month LME contract <MZN0-3> for the fist time since September, suggesting shortages in nearby supply are easing.
ZINC STOCKS: Headline stocks in LME warehouses have fallen to 109,925 tonnes, the lowest since January 2008. <MZNSTX-TOTAL>
RUSAL: Russia's Rusal said it expected aluminium demand to grow in 2019 and saw potential for prices to rise. It said production outside China was flat at 27.6 million tonnes in 2018 while demand rose by 2.8 percent to 30 million tonnes.
METALS PRICES: LME aluminium traded down 0.3 percent to $1,889 a tonne, zinc fell 1.5 percent to $2,691 a tonne and nickel slipped 1.4 percent to $12,800 a tonne. Tin was bid unchanged at $20,950 a tonne and lead traded 0.2 percent higher at $2,085 a tonne.