LONDON, Nov 16 (Reuters) - Copper on Friday was set to end the week nearly 2 percent higher as signs of supply tightness supported prices, but worries about the outcome of a U.S.-China trade dispute limited gains. Supply shortages were also powering zinc towards its biggest weekly gain since September. Benchmark copper on the London Metal Exchange was down 0.3 percent at $6,165.50 a tonne at 1126 GMT but up 1.8 percent this week. Prices rallied after news that Chinese smelter Jiangxi Copper and miner Antofagasta had agreed lower treatment and refining charges for 2019, said ING analyst Warren Patterson. "This is showing that either there is a tightening in concentrate supply or too much spare smelting capacity in China. I think it's a mixture of the two," he said. But while the fundamentals were good for copper, uncertainty about U.S.-China trade talks were weighing on prices, he added. COPPER STOCKS: Headline copper inventories in LME-registered warehouses MCUSTX-TOTAL fell by 5,425 tonnes to 161,025 tonnes, nearing last month's 10-year low of 136,675 tonnes. SPREAD: Another signal of tight supply is the premium of cash copper over the three month contract MCU0-3, which has drifted from a near four-year high of $47 last month to $14 but is still far above recent norms. TECHNICALS: Copper was holding just above its technically important 50-day and 100-day moving averages around $6,160-$6,165. U.S.-CHINA TRADE TALKS: A senior White House official told Reuters a written response sent this week by China to U.S. demands for trade reforms was unlikely to trigger a breakthrough at talks. Worries that rising tariffs could damage China's economy have helped to push industrial metals prices sharply lower in recent months. China is the world's largest consumer of metals. ZINC: Benchmark LME zinc was down 0.3 percent at $2,568 a tonne but up 1.8 percent this week, with stockpiles in the LME's warehouse system falling to a 10-1/2 year low of 125,400 tonnes. MZNSTX-TOTAL SPREAD: The premium of cash zinc over three-month metal MZN0-3 has surged to $74, the highest since October last year, from a discount of more than $20 two months ago, suggesting a shortage of available material. DEFICIT-OUTLOOK: The roughly 13.5 million tonne global zinc market had a 305,000 tonne deficit in the first eight months of this year, the International Lead and Zinc Study Group (ILZSG) said this week. Analysts expect, however, that supplies will increase into next year, keeping a lid on prices. OTHER METALS: LME aluminium was up 0.4 percent at $1,937 a tonne, nickel was 0.9 percent higher at $11,360, lead had gained 2.2 percent to $1,972.50 and tin was down 0.1 percent at $19,380.