President Donald Trump has fired Rex Tillerson as secretary of state — a move that the world found out about through a tweet Tuesday morning.

  • Trump fires Secretary of State Rex Tillerson
  • President says they'd clashed over Iran nuclear deal
  • Trump wants CIA Director Pompeo to succeed Tillerson

The shakeup at the highest levels of the U.S. diplomatic ranks comes as Trump plans to hold talks with North Korean Leader Kim Jong Un.

In the same tweet, Trump said he would nominate CIA Director Mike Pompeo to replace Tillerson.

Tillerson had just returned from a cut-short trip to Africa when the announcement was made, and White House officials said he didn't get to speak with the president before being let go and doesn't know why.

Later Tuesday, two federal officials said one of Tillerson's top aides — Undersecretary of State for Public Diplomacy and Public Affairs Steve Goldstein — was also fired, shortly after he released a statement saying Tillerson was "unaware of the reason" for his firing. Goldstein had also said that Tillerson learned of his firing from Trump's tweet.

Trump said he and Tillerson, a former CEO of ExxonMobil, had been talking about parting ways for a long time and "disagreed on things," singling out the Iran nuclear deal.

"When you look at the Iran deal, I thought it was terrible," Trump said. "He thought it was OK. I wanted to either break it or do something; he felt a little differently. So we were not really thinking the same. With Mike Pompeo, we have a very similar thought process. I think it's going to go very well," Trump said.

In a news conference Tuesday, Tillerson said he's delegating his responsibilties to Deputy Secretary of State John Sullivan for now and will formally step down at the end of the month. He said the State Department "exceeded the expectations of almost everyone" on North Korea.

Reaction to the president's decision wasdivided among lawmakers.

"Mike Pompeo is an excellent choice to lead the State Department and represent the United States around the world. He understands very clearly the international challenges and the opportunities before America in the 21st Century," Florida Sen. Marco Rubio said in a statement.

Meanwhile, New York Sen. Chuck Schumer said: "The instability of this administration in just about every area weakens America. If he’s confirmed, we hope that Mr. Pompeo will turn over a new leaf and will start toughening up our policies towards Russia and Putin."

One of Tillerson's most vocal supporters, Sen. Bob Corker, who heads the Foreign Relations Committee, acknowledged that Trump had Tillerson had disagreed but said the firing caught him by surprise because "they had learned to work together a little bit better."

Trump urged Congress to swiftly confirm Pompeo, and Tillerson also supports the succession.

Information from the Associated Press was used in this report.