(Adds details of mediation talks)
SANTIAGO, Aug 6 (Reuters) - Miner BHP said on Monday that it had formally requested a period of government mediation with the union at its Escondida copper mine in Chile, the world's largest, prompting the union to postpone the start of a strike approved by workers.
The two parties will meet, together with a government mediator, at 9:30 a.m. (1330 GMT) on Tuesday, and talks will continue until Aug. 13, according to an internal union document seen by Reuters.
If there is no agreement by then the strike would begin on Aug. 14, though if both parties agree the talks could be extended by another five days, according to the document.
Earlier on Monday, the union had said in a statement that it had begun preparing for a strike. Workers last week rejected the company's final wage offer and approved a strike, but Chilean law allows either party to call for a period of government mediation, a last effort to reach agreement ahead of a walk-off.
"We have asked authorities for mediation because we want to reach an agreement and because we know that no one wants a strike," said Patricio Vilaplana, BHP vice president for corporate affairs, in a statement.
Last year, a 44-day strike at the mine jolted global copper markets and slowed economic growth in the South American country, which is the world's top copper producer.
BHP's final contract offer two weeks ago included a signing bonus of about $18,000 and a 1.5 percent boost to salaries, with increases for inflation.
But the union had asked for a signing bonus of almost double that offered by the company, and had requested a salary increase of 5.0 percent, leaving a wide gap between the two sides.
Despite the mounting tensions at Escondida, copper prices slid on Monday as investors worried about the damage to global economic growth from the trade dispute between the United States and its trading partners.
Chile increased its copper production to 2.83 million tonnes in the first six months of this year, a 12.3 percent gain on the same period the previous year, Chilean copper commission Cochilco said on Monday.
Escondida produced 925,000 tonnes of copper in 2017.
(Reporting by Dave Sherwood and Antonio de la Jara; editing by Clive McKeef and Rosalba O'Brien)