Copper prices edged up in London on Wednesday as a softer dollar made greenback-priced metals cheaper to holders of other currencies.

Three-month copper on the London Metal Exchange rose 0.2% to $8,309 per metric ton by 0256 GMT, while the most-traded October copper contract on the Shanghai Futures Exchange declined 0.4% to 68,700 yuan ($9,413.80) a ton.

The dollar index edged down slightly ahead of a US Federal Reserve policy meeting later in the day where it is expected to leave the benchmark overnight interest rate unchanged.

However, copper inventories are building in LME-registered warehouses, with stockpiles at 149,600 tons the highest since May 2022, capping gains in prices.

Copper inventories in SHFE warehouses had also been rising for four weeks straight and were at 65,146 tons by Sept. 15, the highest since July 21.

LME aluminium edged up 0.1% to $2,216.50 a ton, nickel rose 0.9% to $20,090, lead increased 0.2% to $2,224.50, zinc fell 0.6% to $2,482.50 and tin eased 0.1% to $26,080.

SHFE aluminium fell 0.4% to 19,190 yuan a ton, zinc dropped 1.2% to 21,535 yuan, nickel rose 1.7% to 164,180 yuan, lead was 0.4% higher at 17,285 yuan and tin climbed 0.5% to 221,350 yuan.

Combined nickel inventories in SHFE and LME warehouses were at 46,055 tons, the highest since March 30.

Copper heads lower ahead of Fed meeting, as inventories build

Lead stockpiles in LME warehouses leaped to 71,050 tons, the highest since July 2021.

SHFE lead inventories climbed to 79,711 tons, a level unseen since September 2022.

Zinc stocks in LME warehouses, however, have been falling to 115,350 tons, the lowest since Aug. 14.