The alliance between South Korea and the United States faces a grave challenge from the evolving nuclear and missile threat from North Korea, Seoul's top diplomat said Monday, adding that it is more important than ever to maintain the allies' cooperation on a unified front.

Foreign Minister Yun Byung-se expressed the concerns during a meeting with 14 U.S. security experts belonging to the Center for a New American Security (CNAS), a think tank established in 2007 by senior defense and diplomatic officials.

The delegation was led by Michele Flournoy, co-founder and chairperson of the CNAS and former undersecretary of defense. She is widely considered the No. 1 candidate for defense secretary under a Hillary Clinton presidency.

"Minister Yun said that the Seoul-Washington alliance faces a grave challenge from the North's nuclear and missile programs and noted that against the grim situations in the wake of the North's fifth nuclear test and continued provocations, the alliance and close coordination between the two countries are more important than ever," the ministry said in a press release.

Yun went on to say that the North's upgrading of its nuclear capability is posing a threat beyond the Northeast Asian region and underlined the need for a unified front in pressuring the North to give up its weapons of mass destruction.

The CNAS experts expressed interest in the ongoing efforts to draft a resolution at the United Nations Security Council after the North's latest nuclear test on Sept. 9 and possible ways to realize denuclearization of the peninsula, among other things. the ministry said.

The foreign ministry expressed hopes that the meeting will help the young, next-generation security experts enhance their understanding of many Korea issues, thereby creating a positive atmosphere in Washington for its diplomatic policies going forward. (Yonhap)