NEW : Spokeswoman says Clapper is standing by his comments on Libya . Graham cited two previous occasions in which Clapper made misstatements , and said his comments on the Libya situation `` should be the final straw . '' NEW : National security adviser : Clapper was giving a `` flat-out resources analysis '' not an opinion piece or anything else '' when he said the U.S. should have done more to prevent attacks in Benghazi and that it would be wrong for him to comment further about what happened there. His statement that China , Russia pose greatest threat to U.S. irks Sen. Carl Levin .
NEW : Spokeswoman says Clapper is standing by his comments on Libya . NEW : National security adviser : Clapper was giving a `` flat-out resources analysis '' not an opinion piece or anything else '' when he said the U.S. should have done more to prevent attacks in Benghazi and that it would be wrong for him to comment further about what happened there. His statement that China , Russia pose greatest threat to U.S. irks Sen. Carl Levin .