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SAN FRANCISCO, Nov 12 (Reuters) - Calpers staffers have urged board members of the biggest U.S. public pension fund to approve plans to reduce the fund's asset exposure to PIMCO by $100 million and to AllianceBernstein Holding LP (AB.N: Quote, Profile, Research) by $478 million, according to documents on its website on Thursday.

The proposed reductions by the staff of Calpers, the $200 billion California Public Employees' Retirement System, are aimed at U.S. high-yield fixed-income funds under management by PIMCO and international fixed-income funds under management by Alliance Bernstein.

The reductions would lower allocations to both of those asset classes by roughly half.

Calpers has about $4.2 billion in international fixed-income assets under management with external managers, with about $978 million managed by AllianceBernstein.

Calpers has about $411 million in U.S. high-yield fixed-income assets under management with external managers, with PIMCO managing about $203.5 million of those assets.

PIMCO also manages about $1 billion of international fixed income assets for Calpers. There was no recommendation to change that arrangement.

Calpers staffers recommended the fund sell $8 billion of assets from its global fixed-income plans over the next 12 months to achieve a 20 percent allocation target for them.

The fund's allocation target in September for its global fixed-income asset class was 24 percent. (Reporting by Jim Christie, editing by Gerald E. McCormick)