"The downgrade to the pension obligation bonds reflects the nature of this type of debt which is unsecured and paid from any of the county's funds, pressured by factors which affect financial performance such as steeply rising service costs," Moody's said in a statement.

"The pension obligation bonds are an unconditional county obligation payable from any legally available funds," Moody's added. "However, the county does not have the ability or authority to raise taxes to meet debt service."