Ambac Financial Group Inc, once one of the largest U.S. bond insurers, said on Monday it may file for bankruptcy protection this year, after missing an interest payment due on some debt.

In a regulatory filing, Ambac said it is in talks with senior debtholders about restructuring its debt through a "prepackaged" bankruptcy filing.

The New York-based company said if it cannot reach agreement on a prepackaged bankruptcy in the near term, it intends