The Pentagon and other U.S. government agencies should complete a legislative proposal in coming weeks to let regulators block proposed mergers for national security reasons, instead of just antitrust concerns, a top official said on Tuesday. Defense Undersecretary Frank Kendall, who oversees arms weapons acquisitions and industrial base issues for the Pentagon, made the comments in an interview, after first mentioning the legislative push in September. In September he raised concerns about further consolidation among the biggest players in the U.S.