UPDATE 1 — BHP's Escondida, supervisors' union avert strike with preliminary agreement

(Adds detail, context) By Fabian Cambero SANTIAGO, Oct 14 (Reuters) — The supervisors' union at BHP's Escondida copper mine in Chile and company representatives have reached a preliminary agreement to avoid a strike, two sources familiar with the negotiations told Reuters on Wednesday. The agreement, which has already been drafted, still needs to be ratified by members of the union in the coming hours, they added. Neither the union nor the company had an immediate comment on the agreement. Talks between BHP and the union started hours earlier, in a last-ditch effort to avoid a work stoppage at the world's largest copper mine. The union had said it was ready to go on strike as early as Wednesday if mediation efforts to tie up a new collective labor contract failed. The possibility of a strike at Escondida has been supporting copper prices as any stoppage would tighten global supply of the red metal. (Reporting by Fabian Cambero. Editing by Mark Potter) ((Aida.Pelaez-Fernandez@thomsonreuters.com;)