Washington - Donald Trump's war of words against his attorney general and one-time ally Jeff Sessions escalated on Monday, raising speculation the president may be preparing the ground to replace him.Trump and his advisers are in fact talking about the possibility of replacing Sessions, The Washington Post reported on Monday evening, quoting people familiar with these discussions.Trump earlier took to Twitter to declare his top law enforcement official "beleaguered" as he wondered out loud why Sessions was not investigating 2016 presidential candidate and former secretary of state Hillary Clinton."So why aren't the Committees and investigators, and of course our beleaguered AG, looking into Crooked Hillary's crimes & Russia relations?" Trump asked.US presidents normally avoid being seen as influential on ongoing or possible investigations at all costs.But it is Trump's comments about his erstwhile friend that have raised eyebrows.Trump has expressed increasing anger with Sessions as his Justice Department's investigations into possible Trump-Russia collusion has quickened.Last week, Trump publicly upbraided Sessions for stepping back from issues related to the probe.Sessions recused himself because of his role on Trump's campaign and because he failed to tell the Senate during his confirmation hearings about contacts he had with the Russian ambassador in Washington.'Unfair to the president'Trump said he would never have hired Sessions had he known he would recuse himself."I think is very unfair to the president," Trump told The New York Times last week. "It's extremely unfair, and that's a mild word, to the president."Sessions has said he had no plans to resign.That increasingly appears problematic for Trump, as he struggles to influence an investigation that has ensnared his eldest son, son-in-law and top aides.In May, Trump fired FBI director James Comey over the bureau's investigation into Russia.That led to the appointment of high-powered special prosecutor Robert Mueller.The Post report said Trump associates see getting rid of Sessions as part of a potential strategy to fire Mueller and end the Russia investigation.Sessions cannot influence the probe because he has recused himself.Shortly after Trump's tweet, the website Axios reported that Trump was considering replacing Sessions with another early supporter, Rudy Giuliani, a former New York mayor.But Giuliani later on Monday dismissed the report and said Sessions was right to have recused himself from the Russia probe, CNN reported.Sessions "made the right decision under the rules of the Justice Department", CNN quoted Giuliani as saying as he arrived at Ronald Reagan Washington National Airport.