Goldman Sachs Group Inc., the fifth-biggest U.S. bank by assets, estimated that its “reasonably possible” losses from legal cases against the firm may amount to as much as $3.4 billion.

The estimate, which includes cases where parties are demanding that Goldman Sachs repurchase securities, was disclosed in the firm’s annual 10-K filing with the Securities and Exchange Commission today.

The estimate is for the “aggregate amount of reasonably possible losses” as of Dec. 31, 2010, the filing said.