(Recasts with comment from miner, new quotes from union)
By Mitra Taj and Patricia Velez
LIMA, Nov 10 (Reuters) - Workers at Peru's largest copper mine began an indefinite strike on Monday, disrupting operations, although the union leading the walkout and the Antamina mine provided differing accounts on the scale of the labor dispute's impact.
Hernan Robles, a spokesman for the SUTRACOMASA union, said production at the mine had been halted and that it would struggle to send copper ore to port for export.
However, a spokesman at Antamina, which had been producing about 30,000 tonnes per month and accounts for almost a third of Peru's copper output, downplayed the strike and said the mine was focused on "maintaining its productive rhythm."
"The stoppage is partial," said Martin Calderon, a spokesman for Antamina. He said output was continuing as expected under a back-up plan but declined to give details.
BHP Billiton and Glencore Xstrata each have 33.75 percent stakes in Antamina, which is also Peru's biggest producer of zinc. Teck Resources holds 22.5 percent and Mitsubishi Corp 10 percent.
Peru is the world's third-biggest copper producer and the metal is a leading source of hard currency. Slipping copper output this year from Antamina, in Peru's central highland region of Ancash, has added pressure as the country's economy expands at its slowest pace in five years.
Talks between the union and management last week ended without an agreement over workers' demands, which include a bonus to offset shrinking proceeds from a profit-sharing plan.
"The mine cannot send mineral to ports through its mineral pipeline or for that matter send shipments," the union's Robles told Reuters by telephone from the mine.
SUTRACOMASA represents 1,630 out of a total 2,860 workers at the mine. (Additional reporting by Marco Aquino; Editing by Richard Lough and Dan Grebler)