U.S. Ambassador to the U.N. Nikki Haley has defended President Donald Trump over his recent “nuclear button” tweet, denying that it hurts Washington’s credibility with its allies and calling such moves necessary to keep North Korean leader Kim Jong Un “on his toes.”

Haley, speaking Sunday on ABC’s “This Week,” was responding to a question about Kim’s New Year’s Day address, in which he claimed that the entire U.S. was in range of North Korean missiles and said that “the nuclear button is always on the desk of my office. They should accurately be aware that this is not a threat but a reality.”

Trump responded with a tweet laying into Kim: “Will someone from his depleted and food starved regime please inform him that I too have a Nuclear Button, but it is a much bigger & more powerful one than his, and my Button works!”

The back and forth has stoked concern, including from former U.S. Vice President Joe Biden, that it only served to escalate the already fraught situation on the Korean Peninsula.

Asked if the president’s tweet had hurt U.S. credibility with its allies, including Japan and South Korea, Haley was firm.

“They don’t wonder if we know what the hell we’re doing,” she said. “I think it’s very clear we do. What they know is we’re not letting up on the pressure. We’re not going to let them go and dramatize the fact that they have a button right on their desk and they can destroy America. We want to always remind them we can destroy you too, so be very cautious and careful with your words and what you do.”

Pressed if she thought the tweet had been a good idea, Haley called it an important part of Trump’s policy of heaping “maximum pressure” on the isolated regime.

“I think that he always has to keep Kim on his toes,” Haley said. “It’s very important that we don’t ever let him get so arrogant that he doesn’t realize the reality of what would happen if he started a nuclear war.”

In an interview Sunday on the program “Fox News Sunday,” CIA Director Mike Pompeo also addressed the storm caused by Trump’s tweet, calling it “consistent” with the United States’ message to North Korea.

“That tweet is entirely consistent with what we are trying to communicate,” Pompeo said. “We want the regime to understand that unlike before, we are intent on resolving this, and it is our firm conviction that resolving this diplomatically is the correct answer.”

But the spy chief also alluded to military action, which the White House has repeatedly said remains an option, saying that it “is prepared to do what it takes to ensure that people in Los Angeles and Denver and New York aren’t held at risk from Kim Jong Un having a nuclear weapon.”

Adam Mount, an expert on North Korea at the Federation of American Scientists, wrote in a tweet Monday that Pompeo had committed “the cardinal sin of extended deterrence.”

“This is Pompeo literally saying, ‘we won’t risk Seattle to protect Seoul’—the cardinal sin of extended deterrence,” he wrote.

Mount told The Japan Times that the language of the Trump White House had “exacerbated fears of ‘decoupling,’ ” or separating, South Korea and Japan from the American alliance architecture.

“Senior officials seem totally unwilling to manage the threat from a nuclear-armed North Korea,” Mount said. “Rather, they insist they won’t tolerate that threat, which is why they are raising the risk of war in the near term. Essentially, the Trump administration is content to raise the risk that allies face because it they wrongly believe it will decrease the risk to American cities.”

In November, North Korea claimed it had successfully tested a new type of intercontinental ballistic missile, called the Hwasong-15, that could reach all of the U.S. mainland.

Amid the soaring tensions, the North and South were set to hold their first formal talks in more than two years on Tuesday in the truce village of Panmunjom. The talks, which have ostensibly been planned to discuss ways to cooperate on the Feb. 9-25 Winter Olympics in the South Korean city of Pyeongchang, could also see the two rivals look at ways to improve overall ties.

South Korea’s top delegate to the talks said Monday that he will seek to discuss ways to resume reunions of separated families and ease military tensions at the meeting, the Yonhap news agency reported.

Asked if the talks were a positive step, Pompeo served up a less-than-enthusiastic response in a separate interview Sunday on the CBS program “Face the Nation.”

“Past history would indicate that this is a feint, this is not likely to lead to any true change” in Kim’s strategic outlook, Pompeo said. “That is, he will continue to want to maintain his nuclear capability. And that the president has said is unacceptable.”

Still, Pompeo admitted that the recent engagement had given the U.S. a clearer picture of the thinking of Kim, who celebrated a quiet birthday Monday, and his inner circle.

“We don’t think Kim Jong Un is getting the straight story from those around him about the tenuous position he finds himself in both domestically and internationally,” Pompeo said. “It is not a good thing, a healthy thing to tell Kim Jong Un bad news.”

North Korea has been subject to crippling rounds of United Nations and unilateral sanctions from the U.S. and its allies over its missile and nuclear programs.

On Saturday, Trump reined in his fiery rhetoric on the North Korean nuclear issue, saying he would “absolutely” be open to talks over the phone with Kim — a reversal from recent comments chiding his secretary of state, Rex Tillerson, for “wasting his time” by pursuing dialogue with Pyongyang.

On the campaign trail before he was elected president, Trump said he would be willing to sit down and talk with Kim over hamburgers.

Asked about the apparent shift, Haley denied any change in thinking by Trump.

“There is no turnaround,” she said. “What he has basically said is yes, there could be a time where we talk to North Korea, but a lot of things have to happen before that actually takes place. They have to stop testing. They have to be willing to talk about banning their nuclear weapons. Those things have to happen.”

Haley said a halt to testing of its nuclear bombs and missiles “for a significant amount of time” was “very important.”

“Then you go and you work toward the next step,” she said. “This is going to be phases. This isn’t going to happen overnight as we’ve seen.”