The city of Houston is suing the union representing its firefighters in a bid to gain the right to negotiate changes to its pension system.

The city, which already has such power concerning the two unions representing other city workers, is seeking changes to employee contributions that have already been put in place for police officers. It said firefighters have refused calls to meet to discuss the issue. Under state law, firefighters cannot be compelled to the bargaining table.

"Litigation is the only remaining option available to the city," said David Feldman, the city attorney. "Instead of Houston determining, or even having a meaningful say about the level of its own contributions to [the pension fund], that decision is being made by people likely to benefit from the decision.  The city is asking the court to declare unconstitutional the laws that allowed this."