WASHINGTON -- Sandy Berger, who was President Bill Clinton's top national security aide, pleaded guilty Friday to taking classified documents from the National Archives and cutting them up with scissors. Rather than the ''honest mistake'' he described last summer, Berger acknowledged to U.S. Magistrate Deborah Robinson that he intentionally took and destroyed three copies of the same document dealing with terror threats during the 2000 millennium celebration. ''Guilty, your honor,'' Berger responded when asked how he pleaded. The charge carries a maximum sentence of a year in prison and up to a $100,000 fine. However, under his plea agreement, Berger...