US President Donald Trump has fired Secretary of State Rex Tillerson, naming CIA Director Mike Pompeo as his replacement.
Thanking Mr Tillerson for his service, Mr Trump tweeted that his new top diplomat would do "a fantastic job".
Mr Tillerson, a former chief executive of ExxonMobil, was only appointed to the job just over a year ago.
The president also nominated Gina Haspel to become the first female director of the CIA.
What did Trump say?
Speaking to reporters outside the White House on Tuesday, Mr Trump said his differences with Mr Tillerson came down to personal "chemistry".
"We got along actually quite well, but we disagreed on things," said the president.
"When you look at the Iran deal, I think it's terrible. I guess he thought it was OK.
"I wanted to either break it or do something and he felt a little bit differently, so we were not really thinking the same.
"With Mike, Mike Pompeo, we have a very similar thought process. I think it's going to go very well.
"Rex is a very good man, I like Rex a lot."
Mr Tillerson is the latest in a long list of senior officials who have either resigned or been fired since Mr Trump took off
What did Tillerson say?
The Department of State said Mr Tillerson had not spoken to the president and was "unaware of the reason" for his firing.
Under Secretary Steve Goldstein said: "The Secretary had every intention of staying because of the critical progress made in national security."
Mr Tillerson was on an official tour of Africa last week when he was apparently caught unawares by Mr Trump's agreement to meet North Korean leader Kim Jong-un.
The top US diplomat's team said he was feeling unwell on Saturday and later in the weekend the state department said he would cut short his tour by a day.
"I felt like, look, I just need to get back," Mr Tillerson told reporters on his plane home, reports the Washington Post.
The 65-year-old arrived back in Washington before dawn on Tuesday to learn he was out of a job a few hours later.
According to a senior White House official, Mr Trump asked for Mr Tillerson's resignation on Friday, but wanted to wait until he came home to make it public.