London copper prices eased on Tuesday as caution kicked in ahead of a US Federal Reserve symposium later this week that could offer more clues about the timeline of the central bank's stimulus tapering plans.

Copper is often used as a gauge of global economic health and a policy tightening might slow a recovery in the world's biggest economy and boost the dollar, making greenback-priced metals more expensive to holders of other currencies.

Three-month copper on the London Metal Exchange fell 0.2% to $9,256 a tonne by 0411 GMT, while the most-traded October copper contract on the Shanghai Futures Exchange rose 1.4% to 68,530 yuan ($10,573.82) a tonne.

"It is all about the US dollar and it will be crucial to hear what Powell says at the end of this week at Jackson Hole," said commodities broker Anna Stablum of Marex Spectron, referring to Fed Chair Jerome Powell's views at the symposium.

FUNDAMENTALS

• LME aluminium fell 0.2% to $2,597 a tonne, zinc rose 0.7% to $2,948 a tonne and lead advanced 0.4% to $2,295 a tonne.

• ShFE nickel increased 1.3% to 142,420 yuan a tonne, tin jumped 1.9% to 236,900 yuan a tonne and lead was up 0.8% to 15,465 yuan a tonne.

• LME cash copper premium to the three-month contract was $27.95 a tonne, its biggest since April 23.

• The global zinc market was under-supplied by 20,200 tonnes in June following a revised deficit of 23,500 tonnes in May, International Lead and Zinc Study Group's data showed.

• One global aluminium producer has offered Japanese buyers premiums of $230 per tonne for October-December primary metal shipments, up 24% from the current quarter, three sources said on Monday.