American International Group’s share slide may prolong the Treasury Department’s ownership of the bailed-out insurer, limiting near-term gains for private investors, Goldman Sachs Group Inc. said.

Michael Nannizzi, a Goldman Sachs analyst, cut his one-year price target for AIG to $27 from $31 in a note to clients yesterday. The insurer has plunged by more than half since Dec. 31 as it paid claims tied to natural disasters, and said it would take charges to bolster reserves for policies sold in prior years. AIG shares advanced $1.02 to close at $23.16.