ANTOFAGASTA, Chile/SANTIAGO (Reuters) - The union for striking workers at BHP Billiton's (>> BHP Billiton plc) (>> BHP Billiton Limited) Escondida in Chile, the world's largest copper mine, said after meeting with the company on Monday that it was open to further conversations that could lead to reopening negotiations.

"At this time, both parties are doing their own evaluation. Depending on the status of that evaluation, this could go forward," union spokesman Carlos Allendes told reporters in the city of Antofagasta.

"We're going to see if that could put in place a dialogue going forward. We're hopeful. We have the willingness, and we're going to wait."

The union was unclear when further conversations might occur, but Allendes said union leaders might sit down with BHP representatives as early as Monday night.

Company representatives could not be reached for comment.

The 2,500-member union at Escondida has been on strike since Feb. 9. Since then, production has been stopped, sending global copper prices higher amid supply concerns.

Workers have maintained three core demands - that benefits in the existing contract not be reduced, work shifts not be made more taxing and new workers receive the same benefits as those already at the mine.

On Thursday, the union invited the company to return to the negotiating table on the condition that BHP give a written guarantee that talks would focus on that trio of demands.

The company agreed but was ambiguous about its commitment to discuss only the union's key issues. Earlier on Monday, union leaders said that they would meet with BHP, despite slamming the company's response as "manipulative."

Union leaders said earlier on Monday that they had received approval from the rank and file to invoke Article 369 of Chile's labour code, if the leaders deem it appropriate.

That would legally halt the current negotiation process and maintain the benefits of the current contract for 18 months, postponing collective wage talks.

Such an agreement is not often invoked by workers, as it delays the one-time bonus typically given to miners when contracts are signed, and appears less likely after the union's most recent remarks.

The union said delaying the wage talks would allow the next round of negotiations to occur under Chile's new labour code, which is set to take effect in April, giving the union more power.

Escondida produced slightly over 1 million tonnes of copper in 2016. Rio Tinto (>> Rio Tinto plc) (>> Rio Tinto Limited) and Japanese companies including Mitsubishi (>> Mitsubishi Corp) have minority interests in the mine.

(Reporting by Fabian Cambero and Felipe Iturrieta; Additional reporting and writing by Gram Slattery; Editing by Cynthia Osterman and Peter Cooney)

By Felipe Iturrieta and Fabian Cambero