Former Secretary of State Rex Tillerson on Monday denied that he undermined President Trump, after former U.N. Ambassador Nikki Haley said in a new book that Tillerson told her he resisted Trump to “save the country.”

“During my service to our country as the Secretary of State, at no time did I, nor to my direct knowledge did anyone else serving along with me, take any actions to undermine the President,” Tillerson said in a statement to The Washington Post.

NIKKI HALEY REVEALS TILLERSON, KELLY PRIVATELY DISCUSSED RESISTING TRUMP: 'IT WAS OFFENSIVE'

“My conversations with the President in the privacy of the Oval Office were always candid, frank, and my recommendations straightforward. Once the President made a decision, we at the State Department undertook our best efforts to implement that decision,” Tillerson said. “Ambassador Haley was rarely a participant in my many meetings and is not in a position to know what I may or may not have said to the President. I continue to be proud of my service as our country’s 69th Secretary of State.”

Haley, in her new book, “With All Due Respect,” claims that both Tillerson and former White House Chief of Staff John Kelly told her they resisted Trump out of necessity and to "save the country."

Haley said that the two men “confided in me that when they resisted the president, they weren't being insubordinate, they were trying to save the country” and how “Tillerson went on to tell me the reason he resisted the president's decisions was because, if he didn't, people would die."

"This was how high the stakes were, he and Kelly told me. We are doing the best we can do to save the country, they said. We need you to work with us and help us do it. This went on for over an hour," she said.

Haley, however, was not impressed with their appeals and said she was so shocked that she didn't speak on the trip back to New York.

"I didn't think the president's advisors were working against him, not directly anyway. But they were definitely working around him. They were stalling, distracting, taking matters into their own hands -- doing anything they could to resist carrying out his policies," she wrote. "They were heading down a very dangerous path."

"What they were doing was disloyal to the president. More important, it was disloyal to the American people who elected him," she wrote.

Kelly later issued a statement to CBS pushing back on Haley’s remarks: “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.”

In the book, Haley takes aim at Tillerson on a number of fronts, calling him “exhausting” to deal with and outlines how they fought on issues such as the withdrawal from the Obama-era Iran deal.

“He was dismissive of my opinions, and he didn’t make any secret about the fact that he believed his views carried more weight,” she writes in the book.

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Haley is being watched closely by political observers for a hint as to her next move since leaving her post at the U.N. last year.

She has shot down “false rumors” that she is in the running to replace Vice President Pence on the Republican 2020 ticket. That was after she muted speculation she would run against her old boss as a primary challenger.

Last month she was featured as a “special guest” at the Trump Victory Committee’s Fall Retreat, and said that Trump’s foreign policy record as one “every American should be proud of.”

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As she promotes the new book, she is giving Trump her backing in his push against House Democrats’ push to impeach him over his dealings with Ukraine.

"No. On what?” she said when asked by CBS News if Trump would be impeached. “You're going to impeach a president for asking for a favor that didn't happen & giving money & it wasn't withheld? I don't know what you would impeach him on."

Fox News' Ronn Blitzer contributed to this report.