In a press conference on August 17, President Moon Jae-in publicly designated North Korea loading a nuclear warhead on an intercontinental ballistic missile (ICBM) as the "red line." The red line refers to the ultimate limit and is the standard that the U.S. uses to determine its military response to an enemy. While answering a question from a reporter, President Moon used this expression to emphasize that North Korea should not carry out any additional nuclear or missile tests.

However, some experts have questioned whether it was appropriate for President Moon, who said, "We will stop a war from breaking out no matter what," to designate the red line, when even the U.S., which has been mentioning military responses, has not clearly defined it.
North Korea has publicly set its national goal at loading nuclear warheads on intercontinental ballistic missiles and positioning these missiles in actual combat, and it is approaching this goal one step at a time. If North Korea deploys an ICBM loaded with a nuclear warhead in actual combat, they will have stepped over the red line designated by President Moon.

But President Moon did not clearly state what he would do if this happens. With wartime operational control still in the hands of the U.S., there is not much that South Korea can do. Thus the president's remarks can clash with his repeated vows of "no war" voiced during the press conference.

Yang Moo-jin, a professor at the University of North Korean Studies said, "We can ask if South Korea will go to war with North Korea, if North Korea loads a nuclear warhead on an ICBM. We can question whether his remarks were diplomatically appropriate."

The U.S. has mentioned expressions suggesting the red line in connection to North Korea's nuclear problem on several occasions in the past two decades, but each time they have stepped back. In 2002, they said North Korea's expelling of the International Atomic Energy Agency (IAEA) inspectors who were to observe the nuclear facilities in Yongbyon, North Korea, would be the final straw, but North Korea still expelled the inspectors. After that, the U.S. said they would not allow the reprocessing of used nuclear fuel. But North Korea reprocessed their used nuclear fuel. Then North Korea's nuclear test was the final limit. But North Korea responded by conducting their first nuclear test in 2006.

Each time the U.S. drew a line, North Korea crossed it as if in protest and it is likely that North Korea may do so again this time. Within the U.S., some voices argue that they should set the red line at North Korea attempting to strike the U.S. mainland by loading a nuclear warhead on an ICBM and at the hermit state handing nuclear materials to foreign governments or terrorist groups (Former National Security Advisor Susan Rice's contribution to the August 11 edition of the New York Times), but the Trump administration has not clearly stated the red line.

President Moon repeatedly emphasized that a war was not an option. President Moon said, "No one can take military action on the Korean Peninsula without the consent of the Republic of Korea. Even President Trump has promised to fully discuss the issue and seek our consent before determining their response to North Korea, regardless of whichever form it may take." As for President Trump's "fire and fury" remark, President Moon said, "He tried to press North Korea by showing his determined resolution. I don't think it necessarily meant that he was determined to take military action." In other words, it was more of a bluff.

President Moon spoke of the need to resume talks with North Korea, yet at the same time said, "We can only set the mood for dialogue if North Korea ceases further provocations." As for the dispatch of a special envoy to North Korea, the president said it would be possible when such an atmosphere is provided and when we could determine that better inter-Korean relations would help resolve North Korea's nuclear issue. In other words, it was not yet the time to consider a special envoy.