* GRAPHIC-2019 asset returns: tmsnrt.rs/2jvdmXl (Adds closing prices)
By Zandi Shabalala
LONDON, July 9 (Reuters) - Copper fell to a three-week low on Tuesday even as talks resumed between the United States and China in an effort to resolve the long-running dispute that has sapped metals demand.
The world's two largest economies have been locked in a bitter trade war for more than a year, disrupting markets and supply chains. A firm deal has yet to be signed despite a series of discussions and ceasefires on tit-for-tat tariffs.
"It's been back and forth for such a long time," said Danske Bank commodities analyst Jens Pedersen. "The market will trade on a deal when and if it happens.
"We need to see some firm agreements. We had the ceasefire, which means things are unlikely to get worse, but they are still quite bad."
Metals were also under pressure from a stronger dollar, making dollar-priced commodities more expensive for buyers with other currencies.
Benchmark copper on the London Metal Exchange (LME) ended 1.2% down at $5,822 an ounce after touching its weakest since June 17.
CHINA: China will investigate state-owned metals conglomerate China Minmetals Corp and chemicals producer China National Chemical Corp in a new round of central government environmental audits, the environment ministry said.
COPPER STOCKS: On-warrant copper stocks available in LME-approved warehouses rose 5,600 tonnes to 260,725 tonnes, their highest since June 2018. MCUSTX-TOTAL
COPPER SPREAD: The discount between LME cash copper and the three-month contract CMCU0-3 hovered around a two-week high at $17.95 a tonne, indicating ample nearby supply.
COPPER CHARGES: China's Jiangxi Copper Co and Tongling Nonferrous Metals Group have signed treatment and refining charges deals with Chilean miner Antofagasta for the first half of 2020 at $64-$70 a tonne and 6.4-7 cents a pound, sources said.
CHILE: Total June copper exports from top producer Chile were down 14% year on year at $2.628 billion. The value of lithium exports hit $76 million, down 23% year on year.
CONGO: Copper production in Democratic Republic of Congo, Africa's top producer, fell 16.2% year on year in the January to May period, while cobalt output slid by 21.5%, the central bank said.
ZINC: The discount between cash zinc and the three-month contract stood at $2 a tonne, down from a premium of more than $160 in May, as supply concerns eased on the LME market. CMZN0-3
Zinc ended 0.7% down at $2,362, having touched its lowest since early January, on expectations of rising supply.
PRICES: Aluminium closed 0.6% down at $1,820 a tonne, lead was up 2% at $1,921.50, tin shed 1.4% to $18,225 and nickel eased by 0.2% to $12,700.
Additional reporting by Mai Nguyen Editing by David Goodman