US Secretary of State John Kerry (C) speaks with South Korean President Park Geun-hye during a meeting at the Blue House in Seoul on February 13, 2014. Kerry arrived in Seoul on February 13 for discussions on North Korea's nuclear programme, a day after high-level inter-Korean talks failed to resolve a row over looming South Korea-US military drills. AFP PHOTO / POOL / Evan VucciEvan Vucci/AFP/Getty Images
US Secretary of State John Kerry (C) speaks with South Korean President Park Geun-hye during a meeting at the Blue House in Seoul on February 13, 2014. Kerry arrived in Seoul on February 13 for discussions on North Korea's nuclear programme, a day after high-level inter-Korean talks failed to resolve a row over looming South Korea-US military drills. AFP PHOTO / POOL / Evan VucciEvan Vucci/AFP/Getty Images

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John Kerry sends warning to Pyongyang

U.S. Secretary of State John Kerry refuses to back down over military training exercises. CNN's Paula Hancocks explains.

John Kerry sends warning to Pyongyang

U.S. Secretary of State John Kerry refuses to back down over military training exercises. CNN's Paula Hancocks explains.