Benchmark copper on the London Metal Exchange was down 0.5% at $5,701 a tonne at 1033 GMT. Prices of the metal used widely as a gauge of global economic health earlier hit $5,640 a tonne, the lowest since June 2017.
"Commodities and producers are being used as proxys for macro economic sentiment. Prices do not reflect fundamentals or fair value," said Bernstein analyst Paul Gait.
"There are question marks over Indonesian (nickel) supplies, it looks like the grace period on the ore ban is coming to an end."
TRADE: U.S. President Donald Trump last week said the United States would impose more tariffs on Chinese imports, while China vowed to fight back, ending a month-long trade truce between the world's two biggest economies.
"The 10% tariff on the $300 billion worth of goods, if imposed, could further reduce China's exports by 2.7% and drag down China's GDP growth by 50 basis points," Citi analysts said in a note.
"China's mid-year politburo meeting emphasised stability and modest stimulus in preparation for a prolonged trade war. But downside risks loom large if said countermeasures are further disruptive, likely leading most commodity prices to our bear case scenario."
China consumes around half of the world's supply of industrial metals.
YUAN: China has also allowed the yuan to breach the key 7-per-dollar level for the first time in more than a decade, in a sign Beijing might be willing to tolerate more currency weakness that could further inflame the trade conflict.
NICKEL: Prices of the stainless steel ingredient hit a two-week high at $14,930 a tonne on the LME, while on the Shanghai Futures Exchange they touched a 4-year high.
The latest trigger is risks to supply from Indonesia.
Three-month nickel was up 3.1% at $14,895 a tonne.
INDONESIA: Throughout 2017, Indonesia issued permits to export more than 22 million tonnes of nickel ore.
Permits typically stand for one year and companies are allowed to renew them. Under current rules, no unprocessed ore exports will be allowed after January 2022.
"Some people say Indonesian may advance the ore ban from 2022 to this year. I'm not sure how true it is, but some investors will gamble on this to buy nickel," said a nickel analyst.
PRICES: Aluminium was down 0.3% at $1,764 a tonne, zinc slipped 0.8% to $2,333, lead fell 0.2% to $1,948 and tin dropped 1% to $16,805.