DENVER, Colorado — An environmental group wants to prevent Xcel Energy from firing up a new coal-fired plant until a lawsuit claiming the pollution levels will be too high can be heard.

WildEarth Guardians filed a motion Wednesday in federal court seeking a preliminary injunction to keep the utility from starting operations at a new unit of the Comanche power plant in Pueblo. Jeremy Nichols of the group's Denver office says the state permit for the unit doesn't require Xcel to cut mercury emissions as much as it could.

The group filed a lawsuit in July, claiming the utility is violating the law by not obtaining approval required by the federal Clean Air Act.

Xcel Energy and state officials have said the plant has equipment to significantly reduce mercury pollution and monitor emissions.