Chinese and U.S. trade teams will hold talks in mid-September before high-level negotiations next month, China's commerce ministry said, adding that both sides agreed to take actual actions to create favourable conditions.
The prolonged trade war has been weighing on global growth and on demand outlook for copper, used widely in power and construction.
The most-traded copper contract on the Shanghai Futures Exchange rose as much as 2.4% to 47,280 yuan ($6,665.91) a tonne, its highest since July 30, before easing to end up 1.7% at the close.
Three-month copper on the London Metal Exchange edged up 0.2% to $5,759 a tonne by 07103 GMT, after advancing as much as 1% earlier in the session to $5,802.50 a tonne, its highest since Aug. 19.
The gains were short-lived as investors worried about slowing demand growth at top copper consumer China, and expectations that the U.S.-China trade talks could once again change directions.
"This will happen again and again," said a copper analyst.
FUNDAMENTALS
* COPPER STOCKS: LME on-warrant copper inventories <MCUSTX-TOTAL>, or those available for delivery, fell to a two-month low of 209,650 tonnes.
* COPPER: Mantos Copper said on Wednesday that it had clinched $250 million in financing to extend the life of its Mantos Blancos copper mine in northern Chile, aiming for an annual production of 52,000 tonnes from the mine.
* NICKEL SPREAD: The premium of LME nickel cash over the three-month contract <MNI0-3> fell further to a three-week low of $15 a tonne, indicating a supply crunch has eased.
* NICKEL PRICES: LME nickel declined 2.1% while Shanghai nickel broke a five-session gaining streak to end down 1.9%.
* TIN: LME tin rose 2.3% while Shanghai tin jumped 3.2% after Yunnan Tin, China's top tin producer, said it was cutting production as part of a joint action by smelters in response to tight raw material supply.
* CHINA TRADE: China's exports likely rose slightly in August as shippers raced to beat new U.S. tariffs but imports contracted for a fourth straight month, a Reuters poll showed, pointing to further strains on the Chinese economy.
* CHINA: China said it will implement both broad and targeted cuts in the reserve requirement ratio for banks "in a timely manner," an indication that a cut in the key ratio aimed at boosting lending could be imminent.
* OTHER PRICES: LME aluminium edged down 0.4% while zinc rose 0.9% and lead advanced 0.9%. Shanghai zinc rose 2.3%, lead increased 0.5% while aluminium eased 0.1%.