BEIJING, June 19 (Reuters) - Copper prices firmed on Wednesday, supported by ore supply shortages and a soft U.S. dollar, but demand concerns in top consumer China capped further gains.

Three-month copper on the London Metal Exchange was up 1.1% at $9,777 per metric ton by 0729 GMT, while the most-traded July copper contract on the Shanghai Futures Exchange was 0.6% higher at 79,040 yuan ($10,891.85) a ton.

Anglo American said on Tuesday copper output at its Los Bronces mine in Chile is expected to fall nearly a third from average historical levels next year as the miner pauses a processing plant for maintenance.

Shortages of mined copper have been a reason for a price rally this year, with record high prices dampening copper demand in China. Disappointing economic data this week has also added to demand concerns.

A fall in China's spot demand triggered rare large-scale exports, pushing LME stockpiles higher, ANZ analysts said in a note.

Copper stocks in LME warehouses rose to the highest level since January on Monday.

Major copper smelters planned to export up to 80,000 tons of copper in June. However, the actual volume could fall below expectations given recent lower export profits, according to the Shanghai Metals Market.

Meanwhile, the dollar recovered some ground on Wednesday after soft U.S. retail sales data reinforced bets of imminent Federal Reserve rate cuts.

A softer dollar makes it cheaper to buy the greenback-priced commodity.

LME aluminium climbed 0.8% to $2,505.50 a ton, zinc advanced 0.9% to $2,864 and lead rose 2.1% to $2,237.50, tin was 0.8% higher to $32,390, and nickel added 0.5% to $17,385 a ton.

SHFE aluminium increased 0.4% to 20,475 yuan a ton, zinc gained 1.6% to 23,835 yuan, and tin moved 0.7% higher at 269,080 yuan, lead was up 3.2% at 19,485 yuan, nickel declined 1.3% to 133,920 yuan.

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($1 = 7.2568 Chinese yuan renminbi) (Reporting by Siyi Liu and Colleen Howe; Editing by Subhranshu Sahu, Janane Venkatraman and Sonia Cheema)