Updated at 6:25 p.m.: Revised to include comment from Tillerson.

WASHINGTON – Former Secretary of State Rex Tillerson is disputing a claim by Nikki Haley, the former U.S. ambassador to the United Nations, that he sought to subvert President Donald Trump’s agenda in an effort to “save the country."

Tillerson, a former ExxonMobil chief executive, told media outlets on Monday that during his tenure as America’s top diplomat, “at no time did I, nor to my direct knowledge did anyone else serving along with me, take any actions to undermine the president.”

“Once the president made a decision, we at the State Department undertook our best efforts to implement that decision,” Tillerson said, according to The Washington Post, adding that “Ambassador Haley was rarely a participant in my many meetings.”

That denial came after reports emerged that Haley, in her new book, said that Tillerson worked with former White House chief of Staff John Kelly to combat Trump’s decisions and that Haley rebuffed their efforts to join their cause.

“Kelly and Tillerson confided in me that when they resisted the president, they weren’t being insubordinate, they were trying to save the country,” Haley wrote in “With All Due Respect,” which is set to be released on Tuesday.

“It was their decisions, not the president’s, that were in the best interests of America, they said. The president didn’t know what he was doing,” she wrote, according to an advanced copy obtained on Sunday by The Washington Post.

Tillerson went so far as to tell Haley that if he didn’t resist Trump’s decisions “people would die,” Haley wrote.

“To undermine a president is really a very dangerous thing,” she wrote, according to the Associated Press, which also obtained an advanced copy. “And it goes against the Constitution, and it goes against what the American people want. And it was offensive.”

The alleged exchange adds another juicy twist to the acrimonious relationship between Trump and Tillerson – a pairing that ended in March 2018 when the president fired Tillerson via Twitter.

The diplomat, while still serving, reportedly called Trump a “moron.” Trump then challenged Tillerson to an IQ test. Tillerson, after being let go, said Trump was an “undisciplined” leader who “doesn’t like to read.” Trump responded by calling Tillerson “lazy as hell” and “dumb as a rock.”

That tit-for-tat appeared to end in December, when Tillerson laughed away his former boss’s insults.

"That must have been an observation of my current state of affairs," the former Exxon chief joked at the annual meeting of the Dallas Citizens Council, noting that he has not been working. "I'm trying to be very lazy these days, but my wife tells me I'm failing."

It’s unclear if Haley’s book will revive the feud.

Trump has not commented on the alleged activity by Tillerson and Kelly, though he took to Twitter on Sunday to tell his followers to get a copy of Haley’s tome.

Kelly, however, has told news outlets that “if by resistance and stalling, she means putting a staff process in place … to ensure the (president) knew all the pros and cons of what policy decision he might be contemplating so he could make an informed decision, then guilty as charged.”