Recently the Asahi News reported the following:
It was understood from made open US diplomatic official telegrams that China and Russia had made repeated criticism at top North Korean officials' friendly relations with Mongolian government after the latter declared in last August its secession from the six-party talks regarding the nuclear issue.
The British Guardian newspaper published the official telegrams of US embassy stationed at Ulan Bator that had been exposed in the Internet by the private site "WikiLeaks". According to it, when Kim Yoniru of North Korea, at that time the Foreign Secretary (now the director of Worker's Party International Department) conferred in regular meetings with Mongolian government in August last year, he declared that "Never return to six-party talks". It led China and Russia to agree with the UN Security Council's resolution to criticize North Korea, and the two countries repeated their criticism three to four times.
In addition, Kim pointed out that China-Russia then supported Japan-U.S.-South Korea, and that the six-party talks "Became 5:1". It was said that "The true intention of the six-party talks is to destroy the North Korea system", and was said that he told "ardently" his agreement to have direct talks with the United States. Mongolia disclosed such a content to the U.S. government.
Last April, after noting the adoption by unanimous approval in Security Council over its chairman's statement that criticized the lunching of ballistic missile, North Korea declared its breaking from the six-party talks. In May two nuclear tests were forced through, then the Security Council adopted the punishment resolution in June.
The documents have shed light on why North Korea carried out two nuclear tests last year, and shows that North Korea distrusted the six-party talks very much.