North Korea’s state media said on Sunday that at a high-level Workers’ Party meeting, leader Kim Jong Un issued "important" guidelines meant to bolster the army and protect national sovereignty.

South Korean and U.S. troops began naval drills on Monday in a show of force partly directed at North Korea amid signs that Pyongyang will soon carry out a threat to conduct its third atomic test.

The region is also seeing a boost in diplomatic activity focused on North Korea’s announcement last month that it will conduct a nuclear test to protest U.N. Security Council sanctions toughened after a December satellite launch that the U.S. and others say was a disguised test of banned missile technology.

Pyongyang’s two previous nuclear tests, in 2006 and 2009, both occurred after it was slapped with increased sanctions for similar rocket launches. As it issued its most recent punishment, the Security Council ordered North Korea to refrain from a nuclear test or face “significant action.”

North Korea’s state media said on Sunday that at a high-level Workers’ Party meeting, leader Kim Jong Un issued “important” guidelines meant to bolster the army and protect national sovereignty. North Korea didn’t elaborate, but Kim’s guidelines likely refer to a nuclear test and suggest that Pyongyang appears to have completed formal procedural steps and is preparing to conduct a nuclear test soon, according to South Korean analyst Hong Hyun-ik.

“We assess that North Korea has almost finished preparations for conducting a nuclear test anytime and all that’s left is North Korea making a political decision” to do so, Defence Ministry spokesman Kim Min-seok told reporters Monday.

The spokesman said he couldn’t disclose further details because they would involve confidential intelligence affairs. Recent satellite photos showed North Korea may have been sealing the tunnel into a mountainside where a nuclear device could be exploded.

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