Secretary of State Rex Tillerson insisted Wednesday that he is not planning to quit, rebutting persistent reports of policy disputes and personal clashes with the White House.

"I have never considered leaving this post," Tillerson said at an extraordinary and hastily called news conference at the State Department.

Tillerson did not directly respond to an NBC News report earlier Wednesday that he had referred to President Trump as a "moron."

"I'm not going to deal with petty stuff like that," Tillerson said, adding that he does not understand what he called a Washington impulse to "sow dissension" and undermine the administration's work.

He called Trump "smart" and committed to American security and the accountability of those around him.

Trump responded quickly on Twitter after Tillerson's appearance: "The @NBCNews story has just been totally refuted by Sec. Tillerson and @VP Pence. It is #FakeNews. They should issue an apology to AMERICA!"

In Las Vegas, after visiting a hospital, Trump told reporters he has "total confidence in Rex. I have total confidence."

State Department spokeswoman Heather Nauert said Tillerson and Trump spoke on the phone immediately after Tillerson spoke to reporters. She characterized the conversation as "good," and said, "They are all good." She said Tillerson intends to stay on the job.

"The secretary never considered resigning from his post," she said, "and for those who want him to do so, go ahead and keep pushing, because that will only strengthen his resolve."

Nauert also flatly denied that Tillerson had ever called Trump a "moron." She said Tillerson did not apologize, and one was not necessary.

"The secretary does not use that type of language," she said. "The secretary did not use that type of language to speak about the president of the United States. The secretary does not use that language to speak about anyone. He did not say that."

Tillerson's public remarks came after months of disagreements between Tillerson and the White House over staffing and administrative matters at the State Department and a disconnect over what Trump saw as Tillerson's conventional approach to policy matters.

Over the weekend, Trump contradicted Tillerson on diplomatic relations with North Korea and its leader. Trump tweeted that the secretary of state was "wasting his time trying to negotiate with Little Rocket Man" — his nickname for North Korea's Kim Jong Un.

The former ExxonMobil chief executive's eight-month-long State Department tenure has been marked by what people close to the situation describe as tension over what Tillerson saw as Trump's impulse to cut him off at the knees on policy initiatives and what the White House increasingly saw as Tillerson's tendency to freelance.

The NBC News report cited Tillerson's growing isolation from the administration and his personal anger at Trump. It quoted sources describing Tillerson as being on the verge of quitting in July. Vice President Pence gave Tillerson a "pep talk" and told him that he needed to move forward with Trump's policies, NBC reported.

Tillerson flatly denied Wednesday that Pence had intervened to talk him out of leaving and said persistent rumors of an impending exit had been "misreported." The rumors were widespread enough to earn a nickname: "Rexit."

Pence spokesman Jarrod Agen said the assertion Pence and Tillerson had discussed his resignation was "categorically false," and said that "at no time did he and the secretary ever discuss the prospect of the secretary's resignation from the administration."

"My commitment to the success of our president and our country is as strong as it was the day I accepted his offer to serve as secretary of state," Tillerson said Wednesday. "President Trump's 'America first' agenda has given voice to millions who felt completely abandoned by the political status quo and who felt their interests came second to those of other countries."

Tillerson said he plans to stay in his job for as long as Trump wants him to.

"I serve at the appointment of the president, and I'm here for as long as the president feels I can be useful in achieving his objectives," he said.

Whispers about Tillerson being on the outs have circulated for months. White House officials have recently groused to associates outside the administration that Tillerson felt too free to speak or act on his own, without White House approval, and about what officials familiar with recent policy discussions called a worsening relationship with national security adviser H.R. McMaster.

Tillerson also raised eyebrows with apparent criticism of Trump's response to a white nationalist rally in Charlottesville in August, which the president said had included many "fine people." Tillerson's pointed remark that "the president speaks for himself" irked Trump, but did not provoke a crisis.

Tillerson, 65, had spent his entire professional career at the company now known as ExxonMobil. An engineer by training, he had no government experience and no relationship with Trump before the newly elected Republican selected him as the nation's top diplomat last fall.

"He loves his country. He puts Americans and America first," Tillerson said of his boss Wednesday. "He's smart. He demands results wherever he goes, and he holds those around him accountable for whether they've done the job he's asked them to do. Accountability is one of the bedrock values the president and I share."

Tillerson entered office as one of the mainstream foreign policy and national security voices around Trump, putting him at odds with Trump's first national security adviser, Michael Flynn, and his former chief strategist Stephen K. Bannon. He also held an uncertain balance of power with Trump's son-in-law Jared Kushner, whom Trump tasked with seeking Middle East peace and described as a key foreign policy adviser.

Tillerson won some policy battles and lost others, most prominently over whether the United States should remain in the Paris climate accord and how to approach the looming threat from North Korea.

Tillerson clashed with other Trump advisers over the administration's approach to the Iran nuclear deal and whether Trump should certify to Congress this month that the landmark agreement is in the U.S. national interest.

Tillerson has argued internally that it is, despite what he calls serious flaws in the deal. Defense Secretary Jim Mattis went public Tuesday with the same argument. But Trump has strongly suggested that he will go the other way and has chafed at being "steered" toward what he views as an inauthentic position, several people familiar with the dispute said.

Tillerson would not say Wednesday whether he agrees with Mattis, whose own position within the administration appears solid.