By JIM SALTERST. LOUIS (AP) â¿¿ Patriot Coal Corp. has asked the U.S. Bankruptcy Court to modify collective bargaining agreements with the United Mine Workers of America, allowing the company to cut health care coverage for retired miners. St. Louis-based Patriot also sought to change wages, benefits and work rules for existing workers in an effort to make the company more competitive, saying in a filing Thursday that the actions are necessary to save more than 4,000 current jobs. Patriot filed for bankruptcy in July, citing exceptionally weak coal markets, increasing costs and "unsustainable legacy liabilities." The company said that since the filing, coal markets have only gotten worse. "Without the cost relief we are seeking, all of these jobs will be lost and it will no longer be possible to provide health care for more than 23,000 employees, retirees and their dependents," Patriot president and chief executive officer Bennett K. Hatfield said in a statement. "Our labor and retiree benefit costs have risen to levels that simply cannot be sustained given the challenges facing the company and our industry." Separately on Thursday, Patriot filed suit against its former parent company, Peabody Energy Corp., also of St. Louis, saying it wants to ensure that Peabody doesn't try to use Patriot's bankruptcy "to escape Peabody's own health care obligations to certain retirees." Union leaders have been anticipating the effort to cut retiree benefits, holding protests in St. Louis last month that drew more than 1,000 people. UMWA President Cecil Roberts called the proposal "unacceptable" and said the loss of benefits would cause financial ruin and threaten the health of thousands of retirees. "This is the path we have been saying Patriot would take from the very beginning of this bankruptcy last July," Roberts said in a statement. "They're demanding massive changes to the collective bargaining agreement, and they want to scrap the health care benefits our retirees earned through decades of blood and toil."