The city of Stockton, California, is set to become the largest city in the United States to file for bankruptcy. On Tuesday, Stockton officials said talks with creditors have broken down at the end of a three-month deadline for a deal to be reached. The city has a long-term debt of $700 million and has already laid off many workers, including a quarter of its police force. City attorneys could file for Chapter 9 protection as early as today.