WASHINGTON (Reuters) - The Pentagon (news - web sites) asked Congress on Tuesday to help shield the U.S. military from environmental lawsuits which defense officials charged were threatening to close hundreds of live-fire training ranges in the country. The Defense Department said it wanted approval of "modest clarifications" in law that would, for example, grant bases three-year exemptions from some provisions of the federal Clean Air Act to allow initial testing of new weapons, such as the planned Joint Strike Fighter. Individual states would have a right to decide whether to accept an exemption. The exemptions, the Pentagon...