The White House on Monday brushed aside charges by retired Marine Gen. Anthony Zinni, former Chief of the US Central Command, that US policies in Iraq have been a failure. Zinni told CBS’ 60 Minutes it was time to change course in Iraq. ‘‘The course is headed over Niagara Falls. I think it’s time to change course a little bit or at least hold somebody responsible for putting you on this course. Because it’s been a failure,’’ he said on Sunday. The White House said President Bush does not look for advice from Zinni. —Reuters