President Donald Trump surprised his allies and critics on Tuesday by firing Secretary of State Rex Tillerson, saying that while the two men worked well together, they did not see eye-to-eye on critical foreign policy questions facing the United States, such as the Iran nuclear deal.

"We got along actually quite well, but we disagreed on things," the President told reporters this morning, specifically noting their differences on how to handle the Iran nuclear deal from the Obama Administration.

"So, we were not really thinking the same," the President added, saying that he has a "very similar thought process" to that of CIA chief Mike Pompeo, who will now take over for Tillerson, if confirmed by the U.S. Senate.

Mr. Trump made the announcement shortly before 9 am on Twitter, moving ahead with a big shakeup in his Cabinet, as he expressed confidence that Pompeo, a former Congressman from Kansas, would be a good fit at the State Department.

"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," Mr. Trump said of the CIA Director in a written statement.

As for Tillerson, he reportedly did not know today would bring his diplomatic career to a sudden end, as the former head of Exxon-Mobil had just arrived back in the United States last night, after a trip to Africa.

Like most others in the diplomatic community, Tillerson learned of the President's announcement on Twitter - he heard from Mr. Trump by phone over three hours later.

"I received a call today from the President of the United States, a little after noontime from Air Force One," Tillerson told reporters gathered in the State Department briefing room, confirming reports that the Secretary of State had learned of his sacking through social media.

"What is most important is to insure an orderly and smooth transition," Tillerson said, as he thanked workers for their support during his time in the job.

In an at times somewhat unsteady voice, Tillerson reviewed his time at the State Department, saying "much remains to be done" in a number of world hot spots, as he also issued another warning about U.S. relations with Russia.

"Much work remains to respond to the troubling behavior and actions on the part of the Russian government," Tillerson said.

"I'll now return to private life," Tillerson added, saying he would officially end his time as Secretary of State at the end of the month, but effectively leave his duties today.

One thing that was missing from Tillerson's remarks was any kind of 'thank you' for the President - other than mentioning the phone call at the start of his statement, Tillerson never said Mr. Trump's name, or referred to him.

Not only was Tillerson fired, but also his chief spokesman, Steve Goldstein, the Undersecretary for Public Diplomacy and Public Affairs, after issuing official statements and tweets which said Tillerson had not been fired directly by the President, but only by Mr. Trump's tweet.

"The Secretary did not speak to the President this morning, and is unaware of the reason," Goldstein wrote about Tillerson's firing.

As for why Tillerson was terminated today, some Democrats in Congress wondered if it had to do with a statement by the Secretary of State on Monday, in which he pointed the finger of blame directly at Russia over the nerve agent attack on a former Russian spy in England - something that the White House refused to do.

"I am concerned by the method and timing of his termination, which may have resulted from crossing Trump by holding Russia accountable for attacks on western democracies," said Rep. Don Beyer (D-VA).

Others were more blunt.

"There is chaos in the Trump administration’s Department of State," said Sen. Bill Nelson (D-FL).

That was echoed by some Republicans as well - this tweet from Rep. Charlie Dent (R-PA), who is not running for re-election this year.

"The firing of Secretary Rex Tillerson demonstrates President Trump’s erratic behavior," said Rep. Tim Ryan (D-OH).

"This is not normal," Ryan added.