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March 20 (Reuters) - Chilean miner SQM and state-run copper producer Codelco said on Wednesday that the companies were extending the deadline to set terms on a partnership by two months to the end of May.

In a separate statement, SQM said board member Xu Tieying would step down on April 24. The announcements come on the eve of an extraordinary shareholders meeting requested by China's Tianqi Lithium Corp, a major shareholder in SQM.

Tianqi, which recommended Tieying for the board, did not immediately respond to a request for comment.

The purpose of the meeting will be to hear about the status of negotiations between SQM and Codelco, as well as "the detail of the actions and contracts that are expected to be carried out and executed."

Chile is the world's top copper producer and second-largest lithium producer. (Reporting by Kylie Madry and Daina Beth Solomon in Mexico City; Alexander Villegas in Santiago Editing by Chris Reese and Bill Berkrot)