Chile's financial regulator had allowed a planned lithium joint venture between SQM and Codelco to proceed without a vote by SQM shareholders.
Portugal already has the largest copper mine in the European Union, operated by Lundin Mining.
Oversupply and weak prices of materials such as lithium, cobalt and rare earths are dampening cash flows of Western start-ups.
Meeting is considered pivotal for the UN body, expected to finalize its decade-long effort to enact regulations by 2025.
