U.S. Secretary of State Rex Tillerson said at a news conference on Wednesday he shares "bedrock values" with President Donald Trump after what he said was an erroneous report indicating he was on the brink of resigning in July.

Tillerson reaffirmed his commitment to the Trump administration in strong terms not long after the publication of the report, which included the allegation he referred to the president as "a moron."

NBC News had reported on Wednesday that U.S. Vice-President Mike Pence and other top officials intervened to persuade Tillerson not to resign during the summer as tensions rose between Trump and the nation's top diplomat.

In July, Pence met with Tillerson in an effort to ease growing discord over policy, NBC reported, citing 12 current and former senior administration officials and other people close to Trump.

"The vice president has never had to persuade me to remain as secretary of state because I have never considered leaving this post," said Tillerson, a long-time Exxon Mobil CEO before his late entry into politics.

"I am here for as long as the president feels I can be useful to achieving his objectives."

Tillerson listed what he saw as some of the accomplishments of the "America First" thrust of the new administration, including the hobbling of ISIS, stronger sanctions on North Korea amid that country's testing of long-range missiles, and pressing the Gulf states to do more to combat terrorism after a visit to Saudi Arabia earlier this year.

Tillerson dismisses 'petty' reporting

The meeting with Pence and others came days after Tillerson, in a session with Trump's national security team and cabinet officials at the Pentagon, openly criticized the president and reportedly called him a "moron," NBC said, citing three officials familiar with the discussion.

"I'm not going to deal with petty stuff like that," Tillerson responded when asked directly if he called Trump by that term, saying that kind of reporting was a part of Washington political culture he did not understand after his private sector experiences.

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Rex Tillerson, seen with James Mattis, praised the work of Trump's team of international advisers. (Aaron P. Bernstein/Reuters)

Later, State Department spokesperson Heather Nauert flatly denied that Tillerson used the term. She also said Tillerson hasn't said sorry to Trump, as no apology was needed.

Pence backed up Tillerson's account by saying the two men never discussed the "prospect of the secretary's resignation from the administration."

"Any reporting to the contrary is categorically false," Pence's statement said.

NBC News stood by its report.

Last week, Trump said via Twitter that Tillerson was "wasting his time" trying to negotiate with North Korea over its nuclear weapons program.

Tillerson, during a trip to China on Saturday, said the United States had direct channels of communication with the North and was probing Pyongyang to see if it was interested in dialogue. He expressed hope for reducing tensions with North Korea, which is fast advancing toward its goal of developing a nuclear-tipped missile capable of hitting the U.S. mainland.

Defence Secretary James Mattis downplayed any tensions or mixed messages on the policy towards North Korea on Tuesday.

"I do not see the divergence as strongly as some ... have interpreted it," Mattis said.

Senator frustrated with treatment of Tillerson

Tillerson in his speech Wednesday said he had developed a strong working relationship with Mattis, and he also praised the efforts of Nikki Haley, U.S. Ambassador to the United Nations.

Sen. Bob Corker, the Republican chairman of the foreign relations committee, said Tillerson "is in an incredibly frustrating place."

Corker, who has criticized Trump's leadership, told reporters that Tillerson "ends up not being supported in the way that I would hope a secretary of state would be supported."

Corker, from Tennessee, who isn't running for re-election next year, said Tillerson, Mattis and White House Chief of Staff John Kelly are "those people that help separate our country from chaos."

It didn't take long to gauge Trump's reaction to Tillerson's speech.

Trump tweeted again as he was set to visit with Las Vegas officials and residents in the wake of Sunday's mass shooting that killed dozens.

After arriving in Nevada, Trump told reporters "he was very honoured" by Tillerson's comments and had total confidence in his abilities, reaffirming his belief the report was erroneous.

Nauert said Tillerson and Trump spoke by phone after the secretary of state's news conference.

With files from Reuters and The Associated Press