By Jonathan Stempel NEW YORK (Reuters) – The U.S. government on Thursday expressed support for New York City’s lawsuit seeking to halt the spread of “ghost guns,” as city and state officials try to hold sellers of the largely untraceable firearms accountable. In a “statement of interest” filed in Manhattan federal court, the Department of Justice expressed “serious concerns” about the proliferation of ghost guns, and said kits containing the weapons’ components are classified as firearms under federal gun control law. “Ghost guns are a major contributor to the ongoing plague of gun violence,” …