Santiago (Reuters) -The union at Chile's Escondida copper mine, the world's largest, signed a deal on Sunday with BHP, ending a strike that could have threatened global supplies of the red metal.

The three-year deal included changes in labour conditions such as "initiatives to optimize shift changes, increase equipment utilization and compliance with the 40-hour law," BHP said in a statement announcing the deal.

An internal union message, reviewed by Reuters, asked members to return to work.

The mine's powerful union had gone on strike on Tuesday over payment disputes and then come to a preliminary agreement on Friday that had suspended the strike.

Earlier in the day the union had sent a memo to members warning it might re-start the strike if the company did not "rectify its position" over contract talks.

BHP's statement didn't provide any further details on the deal with the union. But earlier in the week, sources at the company and the union told Reuters that BHP offered workers around $32,000 as a bonus and an additional $2,000 in soft loans.

BHP had previously offered a $28,900 bonus per worker, compared with the union's demand of 1% of shareholder dividends from the mine, or roughly $35,000 to $36,000 per member.

LME copper prices traded up 1 percent at $9,211 on Monday amid a firmer tone across metals.

(Reporting by Fabian Cambero; Writing by Sarah Kinosian; Editing by Tom Hogue and Shri Navaratnam)