WASHINGTON -- Nine states, including Massachusetts, filed suit against the federal government yesterday challenging new rules that they say do not protect children and expectant mothers from dangers posed by mercury emissions from power plants.

The suit, filed in the US Court of Appeals for the District of Columbia Circuit, criticizes rules announced March 15 by the Environmental Protection Agency as failing to do all the Clean Air Act requires.

New Jersey is leading the coalition of states, which also includes Vermont, Connecticut, Maine, New Hampshire, New Mexico, New York, and California.

''Our ultimate goal is to persuade the court to invalidate the EPA's rules dealing with mercury emissions," New Jersey Attorney General Peter C. Harvey said. ''Our goal is to reduce mercury emissions that we know are harmful to pregnant women and children."