South Korea's President Moon Jae-in on Wednesday left for China on a four-day visit. He will meet his Chinese counterpart Xi Jinping to discuss the North Korean crisis and bilateral issues.Moon and Xi are set to hold their third summit on Thursday, when they are expected to discuss Pyongyang's nuclear weapons program, Efe news reported. They would also discuss ways to improve bilateral relations strained in the wake of the installation of US-built anti-missile system -- the Terminal High Altitude Area Defence (THAAD)-- on South Korean soil.Beijing regards the missile system as a threat to China's internal security.The meeting between the two leaders comes days after North Korea launched its most advanced intercontinental ballistic missile (ICBM) to date, breaking a two-and-a-half-month hiatus on November 29.Moon is accompanied by executives of large South Korean companies, such as Samsung, Hyundai Motor and LG, Yonhap news agency said.