President Donald Trump last night declined to back Rex Tillerson, his embattled Secretary of State, amid reports he is set to sack him within weeks. In what would be the biggest shake-up of his senior team so far Mr Trump was considering a plan to remove America's top diplomat after less than a year, replacing him with Mike Pompeo, the current Director of the CIA. Barring a change of heart by the president, no Secretary of State will have been dismissed sooner than Mr Tillerson for nearly 120 years. A senior former State Department official told The Daily Telegraph: "This is putting Rex Tillerson out of his misery. "He'll go down in history as probably the worst Secretary of State the United States has ever had. It's been a disastrous tenure." Donald Trump, accompanied by Michael Pompeo, left, before speaking at the Central Intelligence Agency in Langley, in January Credit: AP Tom Cotton, a Republican senator and key ally of Mr Trump in Congress, was expected to take over at the CIA in a reshuffle drawn up by John Kelly, Mr Trump's chief of staff. Mr Cotton, 40, would be the youngest ever Director of the CIA. The changes were expected to be made around the turn of the year. There was no immediate comment from Mr Tillerson. Appearing in the Oval Office for a scheduled meeting with the crown prince of Bahrain yesterday, Mr Trump was asked if he would be firing Mr Tillerson. The president would only reply: "He's here. Rex is here." Rumours of Mr Tillerson's impending defenestration had circulated for weeks as his relationship with the president soured and he became increasingly marginalised in the White House. Mr Trump has publicly criticised Mr Tillerson, the former chief executive of Exxon Mobil, for "wasting his time" trying to pursue negotiations with North Korea over its nuclear programme. ...Save your energy Rex, we'll do what has to be done!— Donald J. Trump (@realDonaldTrump) October 1, 2017 And last month it emerged Mr Tillerson had referred to the president as a "moron," and used an expletive in doing so, during a meeting at the Pentagon. Mr Tillerson did not deny making the comment. Mr Trump then suggested both of them should take an IQ test. "And I can tell you who is going to win," the president added. By contrast Mr Pompeo, a former Republican congressman from Kansas, has developed a better personal relationship with Mr Trump, and better reflects his hawkish stances on North Korea and Iran. Mr Pompeo has previously been a vocal opponent of the Iran nuclear deal, defended waterboarding, called for Edward Snowden to face the death penalty, and advocated keeping Guantanamo Bay open. According to officials Mr Pompeo's free-wheeling style when he delivers the president's morning intelligence briefing, three or four times a week, has engaged the president. Nikki Haley, the US ambassador to the UN, had also been viewed as a possible replacement for Mr Tillerson. According to one theory Mr Trump has been reluctant to sack Mr Tillerson sooner and the leaking of Mr Kelly's reshuffle proposal was an attempt by White House officials to force his hand. One administration official said it had become apparent in September that Mr Tillerson would not be a long term appointment. Some decisions requiring the Secretary of State's signature had already been put off until after his expected departure, the official said. Rex Tillerson with Donald Trump Credit: Reuters Mr Tillerson, the former chief executive of Exxon Mobil, had no previous experience in politics before Mr Trump chose him. He immediately set about an overhaul of the State Department, culling large numbers of career diplomats, which left him deeply unpopular there and led to warnings that he was abrogating America's role in the world. This week two retired senior diplomats, Nicholas Burns and Ryan Crocker, wrote in the New York Times that Mr Tillerson was "dismantling" the foreign service. In response Mr Tillerson said: "There is no hollowing out. I am offended when people say we don’t have a State Department that functions." It was unclear whether Mr Tillerson would be attending a meeting of Nato foreign ministers next week in Brussels. Sarah Sanders, the White House press secretary, said: "As the president just said, Rex is here. There are no personnel announcements at this time."