Experts also say that replacing Secretary of State Rex Tillerson with Mike Pompeo, director of the Central Intelligence Agency, could be meant as a warning to Pyongyang that Washington is committed to its maximum pressure campaign and pursuit of complete, verifiable and irreversible denuclearization of the communist state.
While the White House said Tillerson was informed on Friday of his imminent dismissal, the Associated Press reported on Tuesday that White House chief of staff John Kelly called Tillerson on Friday to inform him that a presidential tweet about him may be coming but did not give any more details.
Trump nominated CIA deputy director Gina Haspel to take over as the agency's first female director.
Outgoing Secretary of State Rex Tillerson said Tuesday that he will formally remain the head of the Department through the end of the month.
Trump said Haspel is an "outstanding person".
US-African relations over the last year-and-a-half of the Trump administration have already been a challenge to understand because a lot of the key roles were not filled.
Hours later, Mr Goldstein was sacked, apparently for contradicting the White House version of events.
"Undersecretary of State Steve Goldstein said Tillerson "did not speak to the president and is unaware of the reason", adding that the former Exxon Mobil CEO "had every intention of staying" in the job because he felt he was making critical progress in national security". That should help address the gnawing uncertainty among leaders around the world created by mixed messages from Trump and Tillerson.
Iran agreed before Trump took office to curb its nuclear program in exchange for the easing of economic sanctions. The two men had been fighting during this time, and Tillerson "often seemed out of the loop or in disagreement with the president on major foreign policy decisions".
Tillerson, who was formerly the head of ExxonMobile, was appointed to the position of Secretary of State previous year, and he and the president have had numerous public disagreements.
He also said he was proud that the U.S. "exceeded expectations of everyone" on the campaign to pressure North Korea to denuclearise despite years of continued development in the face of United Nations and USA sanctions. But it is not clear that Haspel has the same close relationship with Trump.
In contrast, Trump said he and Pompeo have "a similar thought process".
Many of Trump's top national security aides, like Tillerson, have argued that the United States is better off with the Iran nuclear deal than without it.
Tillerson had emerged as a vocal critic on Russian Federation - for its role in the annexation of Crimea, support for Syrian President Bashar al-Assad and alleged meddling in the United States election.
On Monday, Tillerson criticised Russian Federation over the poisonings in England of a former spy and his daughter, directly blaming Moscow after White House press secretary Sarah Sanders declined to do so.
Sen. Ron Wyden, a Democratic member of the Senate Intelligence Committee, said on Tuesday he opposed the nominations of both Pompeo and Haspel. "I think hopefully the entire organization learned something from the so-called enhanced interrogation program".
"I will now return to private life, private citizen, a proud American, proud of the opportunity I've had to serve my country", he said.