"However, given North Korea's continual provocations, now is not the right time for dialogue. Rather, it is time to tighten the screws on North Korea with a view to forcing the regime to change its strategic calculation," he added.

In defiance of global warnings, the North conducted its sixth and most powerful nuclear test Sunday, claiming that it detonated a hydrogen bomb that can be fitted onto an intercontinental ballistic missile.

Lim called upon the U.N. Security Council to respond to the North's recent nuclear test with a fresh resolution containing "much tougher measures, corresponding to the magnitude and gravity"

of the provocation.

The vice minister also said that the Seoul government will do its best for "all possible punitive measures" to be taken in close coordination with the international community.

"Pyongyang must know that its wanton behavior will not go unchecked," he warned.

He called on the North to change its provocative behavior so as to create an environment for a "bright" future.

"Let me make it clear. The ball is in Pyongyang's court," he said. "If Pyongyang makes the right choice, we stand ready to offer a brighter future and the window of a new opportunity can be open for them." (Yonhap)