Trump's national security team agrees: North Korea is a grave threat

The ongoing crisis over North Korea's nuclear and missile programs seemed to enter a dangerous new phase this week as the rogue regime claimed it tested its first intercontinental ballistic missile.

North Korea has previously tested ballistic missiles, but this week's test of a longer-range rocket has policymakers from Washington to Beijing very worried about what happens next. The ultimate fear is that the North Koreans could develop a missile capable of carrying a nuclear device and reaching the U.S. mainland.

Full Interview: Defense Secretary James Mattis, May 28

Face the Nation spoke with the central figures on President Trump's national security team in recent months about the threat posed by North Korea. While they varied somewhat in assessing the severity and immediacy of the danger, they all agreed the current path is not sustainable.

Secretary of Defense James Mattis, in a May interview with moderator John Dickerson, didn't mince words, labeling North Korea "a direct threat to the United States."

"They have been very clear in their rhetoric," he said. "We don't have to wait until they have an intercontinental ballistic missile with a nuclear weapon on it to say that now it has manifested completely.

Asked whether the North Korea's missile program has yielded any progress, Mattis replied, "We always assume that, with a testing program, they get better with each test."

John Kelly on North Korea: "They're not much threat right now except in the world of cyber"

And the secretary of defense warned of grave consequences if diplomacy comes up short. "A conflict in North Korea, John, would be probably the worst kind of fighting in most people's lifetimes," he explained. "North Korean regime has hundreds of artillery cannons and rocket launchers within range of one of the most densely populated cities on earth, which is the capital of South Korea."

In an April interview, Homeland Security Secretary John Kelly adopted a slightly less-hawkish tone.

"So long as they're on the other side of the world without a missile and a nuclear weapon to deliver against the United States, they're not much threat right now, except in the world of cyber," he said. "They're pretty aggressive when they want to be in cyber."

But Kelly offered a caveat that seemed to anticipate the developments of this past week. "The instant they get a missile that can reach the United States, and they have a weaponized atomic device, nuclear device on it, we're at grave risk as a nation," he said.

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Secretary of State Rex Tillerson, in an earlier interview in April, discussed his efforts to push China to help resolve the standoff with North Korea diplomatically. He said President Trump and Chinese President Xi Jinping have had "extensive discussions around the dangerous situation in Korea," and he added, "President Xi clearly understands and I think agrees that the situation has intensified and has reached a certain level of threat that action has to be taken."

Tillerson said the U.S. hoped to "work together with the Chinese to change the conditions in the minds of the [North Korean] leadership, and then at that point, perhaps discussions may be useful."

"But I think there is a shared view and no disagreement as to how dangerous the situation has become," he added. "And I think even China is beginning to recognize that this presents a threat to even…China's interests as well."

Rubio warns North Korea "closer" to intercontinental ballistic missile

Some lawmakers in Congress have also sounded the alarm on North Korea. Florida GOP Sen. Marco Rubio told Face the Nation in an April interview that it would pose an "unacceptable risk" for North Korea to possess a missile capable of hitting the U.S. mainland with a nuclear device.

"Can we live in a world where Kim Jong-un possesses not just nuclear weapons, but the ability to deliver those weapons against the continental United States?" Rubio asked. "If the answer is no, then the options -- and the answer is no for me -- then the options before you are truly quite limited. And none of them are good."

"The best possible outcome would be that he walks away from his long-range missile program. We already know he has nuclear weapons," Rubio continued. "The issue here is, can he put it on a rocket and send it and hit the state of California, Arizona, the middle of the country, where you got that e-mail from, and potentially Washington, D.C.? That's an unacceptable risk. That cannot happen."

Tune into Face the Nation this Sunday for more coverage of North Korea, along with the latest political news and analysis.