The United States and China had discussions on the possibility of a regime collapse in North Korea and other contingencies well before the death of former North Korean leader Kim Jong-il, according to a U.S. congressional report.

But it remains unconfirmed whether the two global powers are continuing such sensitive consultations.

"When asked on Oct. 4, 2009, whether the United States and China discussed contingencies in North Korea, (then) Assistant Secretary of State Kurt Campbell acknowledged talks about "every" aspect," the Congressional Research Service, a think tank affiliated with the U.S. Congress, said in a recent report. It did not elaborate.

Washington and Beijing are working together for the denuclearization of North Korea but talking formally on contingencies in Pyongyang is apparently tabooed. China is North Korea's largest benefactor and top communist ally.

Since North Korea purged and executed Jang Song-thaek, the uncle of leader Kim Jong-un, regional powers have faced increasing calls for drawing up concrete contingency plans on the communist regime. Jang was known as a regent for Kim who took power shortly after the death of his father in December 2011.

South Korea and the U.S. emphasize the importance of China's support in dealing with North Korea issues.

"We share the view that it is important to keep China and other related parties closely engaged to achieve substantial progress in the denuclearization of North Korea," South Korean Foreign Minister Yun Byung-se told reporters here after talks with U.S. Secretary of State John Kerry last week.

"In this regard, we agreed to place this issue at the top of our agenda so that we can better cope with the increasing volatility of the nuclear issue arising from the evolving political situation in North Korea," Yun added.

A senior South Korean official said later that Seoul and Washington will deepen consultations on every possibility that could happen in North Korea. China would be welcome in the talks, the official said.

The CRS quoted a Peking University professor well versed in China's policies as saying, "Beijing would not accept an implosion in Pyongyang or watch passively if other countries gain political and military control in North Korea." (Yonhap News)