WASHINGTON (Reuters) - The United States said on Friday it could restart its prosecution of former Mexican defense minister Salvador Cienfuegos, one day after Mexico declined to charge the general whom the U.S. authorities accused of collaborating with a drug cartel. “The United States reserves the right to recommence its prosecution of Cienfuegos if the Government of Mexico fails to do so,” said Department of Justice spokeswoman Nicole Navas Oxman in a statement.