BEIJING (Yonhap) -- A North Korean nuclear envoy attending a security forum in Beijing said Wednesday that the long-stalled negotiations on the North's nuclear weapons program are "dead," dashing hope that Pyongyang might change its course on its nuclear ambition.

Choe Son-hui, deputy director for North American affairs at North Korea's foreign ministry and the North's deputy chief nuclear envoy, made the remarks during the closed-door forum, according to a diplomatic source who attended the forum.

"The six-party talks are dead," Choe was quoted as saying by the source, who spoke on the condition of anonymity because the forum was not open to the public.

It was not the first time that North Korea, which has conducted four nuclear tests since 2006, said the six-party talks were all but dead. Pyongyang has said the country's nuclear program is not a bargaining chip.

However, the remarks by Choe further complicate diplomatic efforts by South Korea, the United States and China to persuade North Korea to abandon its nuclear weapons program.

During a question-and-answer session at the forum, Choe reaffirmed that North Korea will not give up its nuclear ambition.

"We could not give up our nuclear (weapons program), unless the world gives up nuclear (weapons)," Choe was quoted as saying.

Participants at the forum were "frustrated" by the North Korean envoy's remarks, the source said.

Among those attending the Northeast Asia Cooperation Dialogue, which began its two-day run on Wednesday, are Ambassador Sung Kim, a top U.S. envoy on North Korea policy; Kim Gunn, South Korea's deputy chief nuclear envoy; and Wu Dawei, China's chief nuclear envoy.

The forum opened hours before North Korea test-launched two intermediate-range ballistic missiles, in the North's latest violation of U.N. Security Council resolutions that ban Pyongyang from using ballistic missile technology.

The annual forum allows diplomats and scholars from six nations involved in the six-party talks -- South Korea, North Korea, the U.S., China, Japan and Russia -- to exchange views on how to reduce tension on the Korean Peninsula.

During the forum, however, representatives from South Korea, the U.S. and Japan strongly criticized North Korea for launching the missiles, according to the source.

The North Korean envoy did not make any remarks on the missile tests, the source said.

"This conference again displays a big gap between North Korea and the five nations over denuclearization of North Korea," the source said.

Since its fourth nuclear test in January, North Korea has defied U.N. resolutions that ban the North from conducting missile tests using ballistic missile technology.

South Korea's defense officials said the first launch on early Wednesday morning failed, but the second missile reached an attitude of about 1,000 kilometers and flew some 400 kilometers.

If confirmed successful or partially successful, the second test would mark progress made in North Korea's development of mid-range Musudan missiles. Before the latest launch, Pyongyang had launched four Musudan missiles but all ended in failure.

Responding to the North's missile tests, China's foreign ministry spokeswoman, Hua Chunying, urged the "relevant countries"

not to take action that could escalate tensions on the Korean Peninsula.