WASHINGTON (AP) - U.S.-led military action in Libya has bolstered rebels fighting Moammar Gadhafi's forces, but the international operation could continue for months, the Obama administration says. NATO's top decision-making body was to meet Sunday to expand its enforcement of the no-fly zone to include air strikes against Libyan ground targets. The military progress follows deep criticism against Obama from lawmakers upset that the administration hadn't sought greater congressional input on Libya. [...] But asked on ABC's "This Week" if that would mean a U.S. military commitment until year's end, Gates said, "I don't think anybody knows the answer to...