The top nuclear envoys from South Korea, the U.S. and Japan are meeting for talks on North Korea amid worries about the country's atomic weapons programs.

Wednesday's meeting in Seoul comes after North Korea recently claimed it had tested a new type of missile from a submarine and reiterated that it had built a nuclear warhead small enough to be mounted on a long-range missile.

Outside analysts are skeptical about the claims, but believe the North has advanced its nuclear and missile programs since international nuclear disarmament talks stalled in 2009.

Seoul, Washington and Tokyo are members of now-dormant six-party negotiations aimed at ending North Korea's nuclear weapons program in return for aid. Other members are Pyongyang, Beijing and Moscow.