(Corrects paragraph 3 to remove CalPERS CEO comment to CNBC on supporting 2018 pay package after the pension fund clarifies to Reuters it had voted against)

May 29 (Reuters) - The California Public Employees Retirement System (CalPERS) CEO Marcie Frost is planning to oppose Tesla CEO Elon Musk's $56 billion pay package, CNBC reported on Wednesday.

"We do not believe that the compensation is commensurate with the performance of the company," Frost said in an interview to CNBC.

CalPERS is among the top 30 investors of Tesla and owns 9.5 million shares, according to LSEG data. The U.S. pension fund did not immediately respond to a Reuters request for comment.

In a post on X, Musk responded by saying that the U.S. pension fund "broke the deal." "What she's saying makes no sense, as all the contractual milestones were met. CalPERS is breaking their word," he wrote in the post.

Proxy advisory firm Glass Lewis had on Saturday urged Tesla shareholders to reject the pay package.

Musk's pay package, the largest in corporate America, has no salary or cash bonus and sets rewards based on Tesla's market value rising to as much as $650 billion over the next 10 years from 2018.

A Delaware judge rejected the package in January after terming the compensation as "an unfathomable sum" that was unfair to shareholders.

Last month, Tesla asked shareholders to reaffirm their approval for Musk's pay package that was set in 2018. (Reporting by Harshita Mary Varghese and Niket Nishant)