US President Donald Trump has sacked Rex Tillerson as secretary of state, citing differences, and replaced him with Mike Pompeo, CIA director.

The move by Trump is the biggest shake-up of his cabinet since taking office.

"Mike Pompeo, director of the CIA, will become our new secretary of state. He will do a fantastic job," Trump tweeted on Tuesday.

"Thank you to Rex Tillerson for his service!"

According to the Washington Post, Trump asked Tillerson to leave the post last Friday.

Tillerson cut short his trip to Africa on Monday and returned to Washington, DC, prompting questions about his future at the state department.

In a statement on Tuesday, Trump said that "a great deal has been accomplished over the last 14 months" with Tillerson as top US diplomat.

Trump also said on Twitter that Gina Hapsel, CIA deputy director, will replace Pompeo as the head of the agency. He added that she is "the first woman so chosen".

Mike Pompeo, Director of the CIA, will become our new Secretary of State. He will do a fantastic job! Thank you to Rex Tillerson for his service! Gina Haspel will become the new Director of the CIA, and the first woman so chosen. Congratulations to all! — Donald J. Trump (@realDonaldTrump) March 13, 2018

Reports surfaced last October that Trump was looking to replace Tillerson with Pompeo.

Tillerson, a former top executive of the energy giant Exxon, took office on February 1, 2017.

The US president and now-outgoing secretary of state have not seen eye-to-eye on a range of issues, including the Iran nuclear deal and the Gulf crisis.

Who has been fired from or left the Trump administration? Rex Tillerson, Secretary of State, Fired Gary Cohn, Director of the National Economic Council, Resigned Rob Porter, White House Staff Secretary, Resigned Brenda Fitzgerald, Centre for Disease Control and Prevention Director, Resigned Andrew McCabe, FBI Deputy Director, Resigned Omarosa Manigault, Director of Communications for White House Office of Public Liaison, Resigned Tom Prince, Secretary of Health and Human Services, Resigned Sebastian Gorka, Deputy Assistant to the President, Resigned Steve Bannon, Chief Strategist, Resigned Anthony Scaramucci, Communications Director, Resigned Reince Priebus, White House Chief of Staff, Resigned Sean Spicer, Press Secretary, Resigned Michael Dubke, Communications Director, Resigned Walter Shaub, Office of Government Ethics Director, Resigned James Comey, FBI Director, Fired Michael Flynn, National Security Adviser, Resigned Sally Yates, US Deputy Attorney General, Fired Preet Bharara, US Attorney for the Southern District of NY, Fired Katie Walsh, Deputy White House Chief of Staff, Resigned

"We disagreed on things," Trump said outside the White House on Tuesday, adding that the pair "were not really thinking the same".

Tillerson has criticised Saudi Arabia, the United Arab Emirates (UAE), Bahrain and Egypt - which cut diplomatic and trade ties with Qatar on June 5, 2017 - from the onset.

He urged the Gulf states to ease the blockade, which contradicted what appeared to be Trump's initial support for the move.

On the Iran nuclear deal, Tillerson has repeatedly had to dispel speculation that Trump would completely scrap the agreement.

In January, Tillerson said the US was working on a plan "to fix" the accord, which Trump has called the "worst deal ever".

Marwan Bishara, Al Jazeera's senior political analyst, said a country's leader should have advisers with a wide range of views on important issues.

This way, a president may have a complete view of the situation, he said. Tillerson's divergent views were "precisely why he should be in the room".

Tillerson had a steady hand in terms of policy, and "certainly [had] been more steady and more sober than the president", our senior political analyst said.

Juan Cole, a visiting professor at Qatar University, said Trump's move "is not a surprise.

"This is a pattern with Trump," Cole told Al Jazeera.

"When he does not like someone, when he feels the person is not personally loyal to him, he fires him very publicly and in a way to humiliate him."

According to US media, Trump also wanted to have a new team in place before any meetings between the administration and North Korea began.

"The president wanted to make sure to have his new team in place in advance of the upcoming talk with North Korea," AFP news agency quoted an unnamed, senior US official as saying.

Last week, it was revealed that Trump had accepted an invitation to meet North Korea's Kim Jong-un, following a months-long diplomatic standoff that saw the two leaders exchange fiery military threats and personal insults.

Lawrence Korb, a former US assistant secretary of defence, said that Trump's decision to dismiss Tillerson is "evidence of poor judgement.

"It will be very hard for Director Pompeo to be confirmed and be in charge by the time they have this meeting, which will be in less than two months," Korb told Al Jazeera.

"And it's not just a question of Pompeo. The question is what other people do you have? For example, we don't have any ambassador to South Korea yet. The person in the state department in charge of North Korea retired in February."

Iran deal critic

Trump said in a statement on Tuesday that Pompeo has a "proven record of working across the aisle".

He added: "I have gotten to know Mike very well over the past 14 months, and I am confident he is the right person for the job at this critical juncture."

He told reporters outside the White House that he and Pompeo "have a similar thought process".

Pompeo has been a controversial figure since first becoming a Congress member from Kansas in 2010.

In 2013, he was criticised by the Muslim community and others for saying that their silence on violence committed by "extremists" was "deafening.

"Instead of responding, silence has made these Islamic leaders across America potentially complicit in these acts, and more importantly still, in those that may well follow," Pompeo said.

Pompeo has been a staunch critic of the 2015 landmark Iran deal, calling it "disastrous".

Pompeo has called for the scrapping of the deal, saying in October that Iran was "mounting a ruthless drive to be the hegemonic power in the region".

He is known to be one of the most hawkish voices on North Korea in Trump's inner circle, Reuters news agency said.

Pompeo is a graduate of the US Military Academy at West Point and Harvard Law School. He also served as an army officer.

Both Pompeo and Haspel will need to be confirmed by the Senate.