(Bloomberg News) The California Public Employees' Retirement System, the largest U.S. public pension, is seeking to sell about $1.5 billion in private-equity fund stakes as it restructures investments in alternative assets, said three people with knowledge of the matter.

The sale process, which is scheduled to start this week, will be managed by UBS AG, the people said, asking not to be named because the information is private. The assets for sale include a mix of mostly venture capital and buyout funds raised since 2000, two of the people said.

Brad Pacheco, a spokesman for Calpers, declined to comment.

The $234.8 billion pension plan joins private-equity investors including Government of Singapore Investment Corp., manager of more than $100 billion of the country's reserves, and Barclays' pension fund, that are selling stakes to rebalance their portfolios. Investors are trying to free up cash for new funds or reduce their number of managers and concentrate bets with the best performing ones.

Calpers seeks to "rebalance and restructure" its alternative investments this year and next "by adjusting vintage year, geographic and general partner concentration," according to a February presentation.

The Calpers sale will be among the largest deals currently on the secondary market, where investors trade stakes in private-equity funds originally sold by buyout and venture capital firms. The pension's private-equity investments were valued at $33.3 billion as of April 6.

This isn't the first time Calpers has moved large portfolios on the secondary market. The pension fund sold $2 billion of partnerships at the end of 2007, prior to the financial crisis. Calpers last year shopped two other sizable portfolios of private-equity fund stakes. One of these portfolios was the sale of $800 million in buyout stakes to Amsterdam-based AlpInvest Partners NV.

The $1.5 billion portfolio for sale includes entire stakes in funds rather than partial positions, meaning the pension plan is weeding out managers it has decided against investing with in the future, according to the people. In contrast, last year Calpers sold partial stakes in funds and kept relationships with those managers albeit with smaller interests.