State-run JSW and Australia's Prairie, which is developing mines in Poland, have been in cooperation talks for much of this year but JSW wants control.
A vote by the striking workers on whether to accept a new workplace agreement is due to close on Thursday, with the union anticipating a strong "no" vote.
BHP will gain access to SolGold's Cascabel project, in northern Ecuador, believed to have the potential to become one of the largest copper-gold assets ever discovered.