Last year, a more than month-long strike at Escondida ended with workers opting to extend their previous contract through July 31 of this year instead of replacing it.

New negotiations are scheduled for June, but BHP said it hoped to begin earlier.

"This invitation seeks to open a space of dialogue and respect in which the current challenges of the company and the legitimate interest of its workers can be address together," the company said in a statement without proposing a date.

The union summoned its members to an assembly to decide whether to accept the invitation, according the union's website.

In February, the union ruled out early talks amid a dispute with the company over the formation of a competing union at the mine.

Last year's strike jolted the global copper market and cost BHB an estimated $1 billion (£0.8 billion).

(Reporting by Fabian Cambero; Writing by Mitra Taj; Editing by Sandra Maler)

By Fabian Cambero

Stocks treated in this article : BHP Billiton Plc, BHP Billiton Limited