Defense Secretary James Mattis speaks to CBS's "Face the Nation" about the threat posed by North Korea on Saturday, May 27, 2017. The interview aired on May 28.

(CNSNews.com) - “A conflict in North Korea, John, would be probably the worst kind of fighting in most people's lifetimes,” Defense Secretary James Mattis told John Dickerson, host of CBS’s “Face the Nation” in an interview taped on Saturday.

“Why do I say this?” Mattis asked rhetorically. “The 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.

“We are working with the international community to deal with this issue,” Mattis said. “This regime is a threat to the region, to Japan, to South Korea, and in the event of war, they would bring danger to China and to Russia as well.

“But the bottom line is, it would be a catastrophic war if this turns into combat, if we are not able to resolve this situation through diplomatic means.”

On Monday, two days after Mattis spoke to CBS, North Korea carried out yet another ballistic missile launch – at least the 11th this year – this one involving a short-range Scud-class projectile that landed in Japanese waters.

“We always assume that, with a testing program, they get better with each test,” Mattis told “Face the Nation.”

As CNSNews.com reported on Monday, the U.S. and the world are waiting for North Korea to test an intercontinental ballistic missile. Dictator Kim Jong-un announced in January that preparations for test-firing an ICBM had “entered the final stage.”

The big concern is that North Korea is getting closer to the point where it could land a nuclear-armed ICBM on U.S. soil.

Mattis told CBS that North Korea is 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.”

Mattis refused to say what the U.S. might do if North Korea eventually gains the ability to launch a nuke at the United States. “I would prefer not to answer that question,” he said. “The president needs political maneuver room on this issue.

“We do not draw red lines unless we intend to carry them out. We have made very clear that we are willing to work with China, and we believe China has tried to be helpful in this regard.”

President Trump tweeted on Monday: “North Korea has shown great disrespect for their neighbor, China, by shooting off yet another ballistic missile…but China is trying hard.”

Even without successfully testing an ICBM, North Korea is still a “direct threat,” Mattis said, apparently referring to the 23,000-plus U.S. troops stationed in South Korea.

As for a nuclear attack on the U.S. homeland, Mattis refused to say when it could potentially happen: “At this time, what we know, I would prefer to keep silent about, because we may actually know some things the North Koreans don't even know.”