Former U.S. Ambassador to the United Nations Nikki Haley vigorously defended the president Tuesday, telling NBC's "Today" show that the president is a truthful person, and was truthful "in every instance" she interacted with him.

Haley, who is doing the media circuit to tout her new book, "With All Due Respect: Defending America with Grit and Grace," has taken a more vocal stance in defending the president in recent days, shedding some of the caution with which she handled the president publicly as ambassador to the U.N.

On Tuesday, NBC News' Savannah Guthrie asked Haley whether she thinks the president is a truthful person.

Get Breaking News Delivered to Your Inbox

"Yes, in every instance that I dealt with him, he was truthful, he listened and he was great to work with … I never had any concerns on whether he could handle the job ever," she said.

Haley also said she's made up her mind on the impeachment push against the president, lamenting impeachment as "literally the worst punishment" that can happen to a president.

"I have made up my mind. Impeachment is literally the worst punishment you can do to a public official … impeachment is serious. It's the most serious thing you can do to a president," she said. "The other side of this is we are less than a year away from the election. Instead, let the people decide. Let them hear the testimony, that's fine, but let them decide."

Haley did say it's "not a good practice" to ask a foreign leader to investigate a political rival, although she didn't suggest the president had done that in his communications with the Ukrainian president.

Those comments come after Haley told "CBS Evening News" anchor Norah O'Donnell that then-White House chief of staff John Kelly and then-Secretary of State Rex Tillerson had told her they were trying to save the country, and she needed help them.

"Kelly and Tillerson confided in me that when they resisted the president, they weren't being insubordinate, they were trying to save the country," she said. "…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."

Tillerson denied he had ever undermined the president in a sharply worded statement Monday.

"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," he said. "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."

He continued, "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."

Haley addressed that claim again on Tuesday.

"I have always referred to John Kelly as a patriot … but to undermine a president because you think you know better than him is wrong. It's wrong whether it's a Republican president or a Democrat president."