WASHINGTON, - US President Donald Trump on Wednesday called on US Attorney General Jeff Sessions to end federal criminal investigation of whether his presidential campaign cooperated with Russia to influence the 2016 presidential election.After a pair of tweets again attacking the probe by Special Counsel Robert Mueller, Trump wrote: "This is a terrible situation and Attorney General Jeff Sessions should stop this Rigged Witch Hunt right now, before it continues to stain our country any further. Bob Mueller is totally conflicted, and his 17 Angry Democrats that are doing his dirty work are a disgrace to USA!"