Data indicating global copper stocks rose in the three months to March pressured London Metal Exchange three-month copper prices lower Tuesday, traders said.

At late kerb in London, prices were down $259 on the previous day's kerb, but fell even further in post-kerb trading, albeit on thin volume, traders said. After finishing late kerb at $6,740/ton, prices unwound to$6,725/ton in subsequent trading.

A round of LME inventory declines helped copper support prices in morning trading but gains were reversed with news from the International Copper Study Group showing a surplus in March.

International Copper Study Group data showed a surplus of 15,000 tons for March and a 64,000-ton surplus for January-March, rising to 150,000 tons on a seasonally adjusted basis.

Copper needed to close above $7,250/ton for more significant gains to be made, said one analyst.

Aluminium followed copper's cue, falling $68 to $2,480/ton at the late kerb. Zinc fell $75 on the previous kerb to $2,910/ton. Nickel was down $175 on Monday's PM kerb to $19,800/ton.

Volumes remained thin throughout the session, and market participants said liquidity is expected to remain light into next week owing to the U.S. holiday. Traders are also awaiting the U.S. Federal Open Market Committee meeting late Wednesday which is expected to provide fresh trading cues.

3 months metal (prices in dollars a ton)
Bid – Ask, Change from Monday PM kerb

Copper 6740.00-6750.00, Dn 259.00
Lead 965.00-965.50, Dn 12.00
Zinc 2910.00-2920.00, Dn 75.00
Aluminium 2480.00-2485.00, Dn 68.00
Nickel 19800.00-19850.00, Dn 175.00
Tin 7850.00-7950.00, Dn 25.00