US Secretary of State Rex Tillerson says he has never considered quitting, and denied referring to President Donald Trump as "a moron".
Mr Tillerson gave an impromptu statement on Wednesday after NBC News reported the former Exxon Mobil CEO was on the verge of resigning this summer over mounting policy disputes with the White House.
NBC said the tensions came to a head around the time Mr Trump gave a politicised speech in July to the Boy Scouts of America, an organisation Mr Tillerson once led.
"President Trump's foreign policy goals break the mold of what people traditionally think of what is achievable," Mr Tillerson said.
His clear objective was to "dispel with this notion that I have ever considered leaving."
"There has never been consideration in my mind to leave," he added.
Mr Tillerson's denial lead to Mr Trump tweeting that NBC should apologise to the whole country for the "fake news".
NBC also said Mr Tillerson referred to the president as a "moron" after a July 20 meeting at the Pentagon with members of Mr Trump's national security team and Cabinet officials.
NBC cited three anonymous officials familiar with the incident.
Asked about the report, Mr Tillerson replied, "We don't deal with that kind of petty nonsense".
"I'm just not going to be part of this effort to divide this administration."
A State Department spokeswoman has since denied Mr Tillerson referred to Mr Trump as a "moron".
Earlier NBC's claims lead to a Twitter rebuttal by Mr Trump, who labelled them "more dishonest" than his usual media target CNN.
NBC News said it stood by its reporting.
It comes three days after Mr Trump his chief diplomat is "wasting his time" trying to negotiate with North Korea about its nuclear and missile programmes.