SANTIAGO, March 22 (Reuters) - China's Tianqi Lithium Corp on Friday said a number of aspects of a deal being negotiated by Chile's SQM with state-run copper miner Codelco still are not clear.

Tianqi holds about a 20% stake in SQM, which on Thursday told shareholders that talks were ongoing with Codelco over a new lithium partnership.

"The meeting has allowed us to confirm that there is still a considerable amount of fundamental aspects of the agreement that are not defined or have not been clearly explained," Tianqi said in a statement. It said the issues appear to affect SQM's full operation, not only the unit responsible for lithium extraction in Chile's Atacama region.

Tianqi called for shareholders to vote on the final deal to ensure transparency and full participation.

"It is indispensable that the agreement that is reached between SQM and Codelco is approved by the shareholders," the company said.

SQM did not immediately respond to a request for comment.

SQM and Codelco had been set to announce final terms by March 31, but on Wednesday they

extended the deadline

to the end of May. (Reporting by Daina Beth Solomon and Alexander Villegas; Editing by Anthony Esposito and Leslie Adler)