"While supporting South Korea's position and opposing North Korea's nuclear development, President Moon explained his own policy of employing both sanctions and dialogue at the same time to help resolve the North Korean nuclear issue", Yoon said.
"Sanctions against North Korea are also a means to bring the North to the negotiating table aimed at eliminating its nuclear weapons", Yoon told a briefing, adding that Xi indicated his agreement.
North Korea's UN Mission said the organisers infiltrated "the terrorist" into the country with several pieces of satellite communications equipment so he could be updated "with the operational code of terrorism against the supreme leadership, various terrorist methods of using biochemical substances, ways of bribing and hiring the one who would actually carry out the terrorist act and ways of entering the venue of the event".
President Moon Jae-in spoke over the telephone on Thursday with Japanese Prime Minister Shinzo Abe and hinted at scrapping an agreement for compensating the Korean victims of sex slavery during World War II.
U.S. officials have said they see no value in resuming global talks with North Korea under current circumstances and that Pyongyang must make clear it is committed to denuclearization.
Moon has previously expressed ambivalence over the THAAD system and told Xi he was "well aware" of Chinese concerns about it.
The statement said the organisers also gave him instructions to report on the "creed" of the person who would carry out the attack "and the state of his 'brainwashing", and to make sure the preparations were flawless, as there could be a war if it was revealed that South Korea's intelligence agency backed the operation.More news: Abby Lee Miller Says She Feels "Peaceful" After Prison Sentencing
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North Korea's United Nations mission on Thursday said the plot was a "declaration of war".
"With regard to the presidential campaign pledges on the defense sector, of course, we are reviewing conditions and ways for implementation", Moon Sang-gyun, a spokesman for the Ministry of National Defense, told reporters.
China says the Terminal High Altitude Area Defense (THAAD) undermines its security as its powerful radar can probe deep into its territory.
Moon said he will send a delegation to Beijing to discuss both North Korea and THAAD.
Moon responded that he would strive to find an appropriate solution.
"The new South Korean government will actively communicate with China on these issues and seek appropriate resolutions", the statement quoted Moon as saying.
China has denied it is retaliating against South Korean businesses.