States and cities could be forced to report at least half a trillion dollars of additional costs on their books under proposed rules that would shine a harsher light on the growing expense of retired workers' health insurance and other benefits.

The proposals, unveiled Monday by an accounting-standards group, would require state and local governments to add retiree-benefit promises to their balance sheets, making governments' overall financial position appear worse. In addition, many governments would have to change the way they calculate their benefit obligations in a way that could make their shortfalls appear bigger than they do now.

The move by the Governmental Accounting Standards Board is intended to give taxpayers, policy makers and investors more information about the toll that retirees' promised benefits will take on states' and cities' finances. The proposals wouldn't require governments to raise more money to pay for retiree benefits, and they wouldn't force governments to change the level of benefits they provide.

"It will provide a better picture of the cost and liabilities for these benefit promises," said GASB Chairman David Vaudt.

The proposals come as governments grapple with rising costs for current and retired workers. Some states have been racked by legislative battles over how to trim costs. Several municipalities, including Detroit and Stockton, Calif., have filed for bankruptcy protection in recent years amid retiree-benefit burdens, among other issues.