SANTIAGO, April 23 (Reuters) - Chile's government is expected to receive 85% of "associated benefits" including taxes and lease payments from a planned partnership between state-run copper miner Codelco and lithium company SQM from 2031, Codelco Chairman Maximo Pachecho said at an event on Tuesday.

The two companies are negotiating the details of the agreement to partner on lithium mining in the Atacama salt flat, with a May 31 deadline to reach a final deal.

The agreement outlines that 70% of benefits will be allocated to the state from 2025 to 2030, Pacheco said. (Reporting by Daina Beth Solomon; Editing by Tom Hogue)