Donald Trump has sacked Rex Tillerson as his secretary of state and will replace him with CIA director Mike Pompeo.

The US president asked Mr Tillerson to step aside after months of speculation that the pair had fallen out.

The move amounts to a major shake-up in Mr Trump’s national security team and comes despite denials in the past from the president that he wanted Mr Tillerson gone.

It triggered a war of words within the US government as the State Department accused the president of not talking to Mr Tillerson before the sacking.

Mr Trump cited the pair’s differences on the Iran nuclear deal, which the president wants to scrap, when asked about the reason for the change.

The announcement comes just hours after Mr Tillerson went substantially further than the White House in linking the UK spy poisoning to Russia.

CNN reported that Mr Tillerson found out about his sacking from Mr Trump's tweet on Tuesday. He had just returned from diplomatic trip to Africa.

Steve Goldstein, the under secretary of state, released a statement saying Mr Trump had not called Mr Tillerson about the sacking. Mr Goldstein was fired just hours after releasing the comment.

John Kelly, Mr Trump's chief of staff, informed Mr Tillerson he would be replaced on Friday, according to reports sourced to White House officials.