South Korean President Moon Jae-in urged defense officials to step up military reform in case the North “crosses the line,” local media reported Monday.

Moon told officials to “strongly push” for the military to “meet the requirements of modern warfare so that it can quickly switch to an offensive posture in case North Korea stages a provocation,” according to South Korean news agency Yonhap.

North Korea, according to South Korea and the U.S. military, launched several short-range missiles Saturday, though one is believed to have exploded immediately. The pariah state has said little about the success of the event, a change from its frequent inflammatory rhetoric over tension on the Korean peninsula.

But, the North did send a letter to the United Nations Security Council (UNSC) Friday expressing anger at joint military drills between South Korea and the U.S. earlier last week. “The danger of nuclear war is created by the U.S.” and its “evil intention,” the letter said, also accusing the UNSC of being “reduced into a marionette” of the U.S. should it ignore the North’s request for emergency discussions.

“The U.S. shall be held totally accountable for the catastrophic consequences to follow,” the letter threatened.

Moon began his presidency by positing Seoul as open for negotiations with Pyongyang, to little avail from North Korean Supreme Leader Kim Jong-un’s administration.

Robert Kelly, associate professor at Pusan National University, explained to CNBC’s Squawk Box Asia that the “prestige of negotiating directly with a superpower is something North Koreans really, really want.”

But, “There’s no way the U.S. is going to give that to North Korea without some really significant concession,” he added.

U.S. Secretary of State Rex Tillerson said in an interview with Fox News over the weekend that the U.S. would uphold “peaceful pressure” on North Korea, while also working with regional superpower China to “bring the regime in Pyongyang to the negotiating table.”

Julia Coym, senior analyst for north east Asia at consultancy firm Control Risks, told CNBC via e-mail that while some were hopeful that the nuclear threat from North Korea had lessened from recent warnings that it would strike the Pacific island of Guam, talks were unlikely to make progress in the coming year should they resume.

“At the end of the day, Pyongyang remains highly unlikely to relinquish its nuclear or missile program and the U.S. is extremely unlikely to recognize the North as a nuclear power,” she said.

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