The latest tantrum out of North Korea …

(Reuters) – North Korea threatened to attack rival South Korea if Seoul joined a new round of tightened U.N. sanctions, as Washington unveiled more of its own economic restrictions following Pyongyang’s rocket launch last month.

Speaking in Beijing, U.S. Special Representative for North Korea Policy Glyn Davies said he found North Korea’s rhetoric “troubling and counterproductive,” and that he and his Chinese counterparts had agreed a new nuclear test would be harmful.

North Korea threatens war with South over U.N. sanctions