"We are facing the continuing advancement of North Korea's nuclear and missile capabilities," Hwang Joon-kook, South Korea's special representative for Korean Peninsula peace and security affairs, said on Wednesday before the meeting with Sung Kim, the US special representative for North Korea policy, and Junichi Ihara, a regional director-general in the Japanese Foreign Ministry.
The one-day meeting in Seoul came after Pyongyang announced on May 9 that it had successfully conducted an underwater test-fire of a ballistic missile, describing it as a "world level strategic weapon.”
However, some Westerners have questioned the authenticity of the photos released by North Korea following the test.
Seoul, Washington and Tokyo are members of now stalled six-nation negotiations aimed at ending North Korea's nuclear program in return for aid and political concessions.
The six-party negotiations, which included Russia, China, the United States, Japan, South Korea and North Korea, stalled in April 2009 after the United Nations imposed tougher sanctions on Pyongyang for conducting nuclear and missile tests.
North Korea is under UN sanctions over launching rockets considered by the West as ballistic missiles aimed at delivering nuclear warheads.
Pyongyang says its numerous missile tests, slammed mainly by the US and South Korea, seek to boost the North's defense capabilities in the face of enemy threats.