Copper ticked up on Friday and was set for a ninth straight weekly increase, after a string of withdrawal requests from London Metal Exchange warehouses raised availability concerns.
Benchmark three-month copper on the LME was up 0.22% at $14,314.5 a metric ton by 0315 GMT, rising 0.7% so far this week.
The most-traded copper contract on the Shanghai Futures Exchange edged 0.4% higher to 108,820 yuan ($16,191.77) a ton.
"Copper prices have been supported this week by another large increase in LME warrant cancellations," said Craig Lang, principal analyst at information provider CRU.
This week's spree of LME copper warrant cancellations, meaning metal earmarked for withdrawal from warehouses, offset much of the stock gains from big inflows last week.
Available copper in LME-registered warehouses was at 107,050 tons on Thursday, exchange data showed, down from 166,775 tons a week earlier.
Outflows from LME and SHFE warehouses and into U.S. ones ahead of a potential U.S. tariff on imports of refined copper have raised concerns about availability.
Zinc, also supported by falling warehouse stocks this week, was up 0.73% on the LME, but down 0.3% on the SHFE on Friday.
Chinese zinc exports have helped cool fears of a shortage outside the country, even as supply tightness and speculative positioning continue to support prices.
"LME inventories are low, and treatment charges remain deeply negative, highlighting tight concentrate supply and pressure on smelter margins," analysts from ING said in a note.
The cash-to-three-month LME zinc was in a sharp $231.75 backwardation on Thursday, signalling tight availability.
Among LME metals, aluminium dipped 0.08%, lead eased 0.08%, nickel slipped 0.14% and tin was down 0.12%.
Among SHFE metals, aluminium added 0.46%, lead gained 1.06%, nickel lost 0.38% and tin rose 0.61%. ($1 = 6.7207 Chinese yuan)
