Workers ended their lengthy stand-off last month, triggering a law that pushed back pay negotiations by 18 months. Earlier this month, Rio Tinto also reported a plunge in copper output due to the strike in Chile, where it has a 30 percent interest. BHP said in a quarterly report it had "initiated the divestment of non-core acreage" in its shale fields in the US, just weeks after rejecting an activist hedge fund proposal to restructure the business and spin off its US petroleum arm. The sale of 50,000 acres (20,234 hectares) in Hawkville was "well advanced", the miner said, adding that it was "considering all options" including the sell-down of its Fayetteville gas assets. "Everything we do at BHP Billiton is designed to create value for all of our shareholders, today and for the long term," chief executive Andrew Mackenzie said.