Copper prices in London were on track for their first quarterly loss since March 2020 as the prospect of the US Federal Reserve scaling back its pandemic stimulus put pressure on the metal often used as a gauge of global economic health.

Talks of policy tightening in the United States have boosted the dollar, making greenback-priced metals more expensive to holders of other currencies.

Three-month copper on the London Metal Exchange edged up 0.2% to $9,168 a tonne, as of 0420 GMT on Thursday, but lost 2% so far this quarter.

The most-traded November copper contract on the Shanghai Futures Exchange was down 0.7% at 68,160 yuan a tonne.

Losses were limited as Rio Tinto Plc declared force majeure on some copper cathode contracts after shutting the smelter at its Kennecott mine in the United States following an accident last week.

"Prices have edged lower, but they have not collapsed since the highs reached in May and we expect prices to trade sideways over the coming months ... Prices continue to remain elevated on the back of tight inventories," Fitch Solutions said in a note.

Copper inventories in ShFE warehouses dropped to a 12-year low, further supporting metal prices.

Fitch Solutions revised up their copper price forecasts for 2021 to $9,200 a tonne from $8,700, and raised their 2022 prices estimate to $8,800 a tonne from $8,370.

Despite falling 1.2% to 271,400 yuan a tonne, ShFE tin was on track for its best quarter on record, up 31.3%. LME tin was set for its sixth straight quarterly gain.

Aluminium and zinc prices in both London and Shanghai were on track for their sixth straight quarterly gain.