According to the Washington Post, Trump last Friday asked Tillerson to step aside, leading him to shorten his trip to Africa and return to Washington on Monday.
In November 2017, the New York Times reported that Tillerson, who had a rocky relationship with Trump, was on the way out. And Pompeo would be the likely replacement.
Tillerson dismissed the notion as “laughable” as Pompeo remained silent.
On Tuesday, Trump told reporters about their divergent opinions on the Iran nuclear deal. Iran agreed before Trump took office to curb its nuclear program in exchange for the easing of economic sanctions. The president regularly criticizes the agreement as a bad deal and has repeatedly threatened to end it.
Trump spoke Tuesday of his desire to break the deal, but noted that Tillerson "felt a little bit differently, so we were not really thinking the same."
The official’s departure has been widely anticipated for months, but associates said he sought to finish out the year “to retain whatever dignity he could,” the New York Times reported last year.
His exit would make his time as secretary of state the shortest of those whose tenure was not ended by a change in presidents in nearly 120 years.
The relationship between Tillerson and Trump has been strained by name-calling and public disagreements on multiple major issues.
Here are 5 times Trump and Tillerson publicly disagreed on an issue
1. When Trump criticized Tillerson’s approach to North Korea and “Little Rocket Man”
In October, President Donald Trump publicly contradicted Tillerson’s stance on a North Korea and tweeted that Tillerson was “wasting his time trying to negotiate with Little Rocket Man,” Trump’s nickname for North Korea leader Kim Jong Un.
"Save your energy, Rex, we'll do what has to be done," Trump wrote, and warned of U.S. military action to the country's escalating nuclear threat.
Trump also told reporters during a photo op at his Bedminster, New Jersey golf course: “As I said, they will be met with fire, fury and frankly, power – the likes of which the world has never seen before.”
This was one day after Tillerson, who would rather avoid military use to reach a consensus with the country, said he was trying to open the door for talks with North Korea.
Others in Congress also spoke against Trump's approach.
“North Korea is a global threat that requires American diplomacy,” said Rep. Betty McCollum (D-Minn.), who labeled Mr. Trump’s talk “dangerous and risks war.”
2. When the U.S. pulled out of the Paris climate accord
In August, Tillerson publicly disagreed with Trump’s decision to withdraw from the Paris climate accord, a pact to voluntarily curb greenhouse gas emissions.
» RELATED: What is the Paris climate agreement? 9 things you should know
"I was free to express my views. I took a counter view to the decision that was made," Tillerson said.
The United States is now the only country that has rejected the global pact, according to the New York Times.
3. When Trump blamed “both sides” for the deadly Charlottesville, Virginia white supremacist rally
Following the Charlottesville, Virginia rally of white supremacists that resulted in the death of rally protester 32-year-old Heather Heyer, Trump blamed “both sides” for the deadly violence.
Heyer was killed when a neo-Nazi drove a car into her and other demonstrators at the rally.
The president's comments were widely criticized. United Nations experts, without explicitly naming Trump, said it was "a failure at the highest political level of the United States of America to unequivocally reject and condemn racist violence," the NY Times reported.
Amid the backlash to Trump’s comments following the attack, Tillerson addressed State Department interns and staff and said, “We do not honor, nor do we promote or accept, hate speech in any form,” Mr. Tillerson said at the event. “Those who embrace it poison our public discourse, and they damage the very country that they claim to love.”
When asked whether Trump’s response represented “American values,” Tillerson said on Fox News, “The president speaks for himself ... I have spoken. I have made my own comments as to our values as well in a speech I gave to the State Department this past week.”
4. When Tillerson undercut Trump’s Afghanistan strategy
During an address to military personnel in August, Trump repeatedly said the U.S. would win the war in Afghanistan and do so by military action.
"Our troops will fight to win. We will fight to win," he said during an address to military personnel in August. "From now on, victory will have a clear definition: attacking our enemies, obliterating ISIS, crushing Al Qaeda, preventing the Taliban from taking over Afghanistan, and stopping mass terror attacks against America before they emerge."
Tillerson’s approach to the Taliban was more diplomatic and undercut Trump’s.
"You will not win a battlefield victory. We may not win one, but neither will you," he said, addressing the Taliban."So at some point, we have to come to the negotiating table and find a way to bring this to an end."
" A clear victory," the Washington Post's Aaron Blake reported, "is something that basically any military expert will tell you is very difficult to foresee (much less predict) in Afghanistan — especially with only a few thousand more troops on top of already-far-reduced troop levels and an apparently limited amount of patience from the commander in chief."
5. General concern (or lack of) for Russia’s meddling in the 2016 election
Despite growing evidence from the U.S. intelligence community of Russian interference in the election, Trump has repeatledly dismissed or minimized the findings, circling back to U.S. intelligence’s failure 15 years ago regarding Iraq’s weapons of mass destruction to increase doubt about the agencies’ conclusions.
"I remember when I was sitting back listening about Iraq, weapons of mass destruction. How everybody was 100 percent sure that Iraq had weapons of mass destruction. Guess what? That led to one big mess," Trump said. "They were wrong and it led to a mess. So, it was Russia. And I think it was probably others also. And that's been going on for a long period of time."
Tillerson, on the other hand, is concerned about Russian interference. He has said he's tried "to help [the Russian government] understand just how serious this incident had been and how seriously it had damaged the relationship between the US and the American people and the Russian people."
At the G20 summit in Hamburg, Germany in July, Tillerson told an associate he was "stunned" by the way Trump had approached Russian President Vladimir Putin on the issue, the NY Times reported.
Trump said he started his meeting with Putin by saying, "I'm going to get this out of the way: Did you do this?" According to Russian Foreign Minister Sergey Lavrov, Trump accepted firm assertions from Putin that it is not true.