South Korean President Park Geun-hye asked Chinese President Xi Jinping on Wednesday to help persuade North Korea not to carry out a fourth nuclear test, her office said Wednesday, as fresh intelligence suggested that Pyongyang is fully ready for a test. Park made the request in a phone conversation with Xi, saying an additional nuclear test by the North would fundamentally change the security landscape in Northeast Asia as it would spark an arms race and a "nuclear domino" effect in the region, according to her office.