Campbell, who arrived in Seoul on Tuesday visited South Korea´s nuclear envoy Wi Sung-lak and Foreign Minister Yu Myung-hwan to hold discussions aimed at prodding the North back to nuclear talks after the state last week raised tensions by firing artillery toward a disputed sea border with the South.

Campbell said on Wednesday that sanctions against North Korea would continue until the reclusive country returns to six-way talks to discuss disarmament of North Korea´s nuclear weapons.

North Korea in recent weeks has called on the United States to hold talks on replacing the ceasefire that ended the Korean War, while at the same time making military threats to U.S. ally South Korea.

Analysts see this as a ploy by Pyongyang to win concessions to lure it back to the bargaining table and put pressure on Washington for direct talks on a peace deal that can help open the door to international finance for the North.

North and South Korea are still technically at war since the 1950-53 Korean War ended in a truce without a peace treaty.