However, intransigence of China and brazenness of N. Korea could force his hand. In China's case, they may resort to stalling and dragging their feet, while encouraging appeasement crowd in Foggy Bottom to step up and ultimately neutralizing any decisive resolution.
I think he doesn't want to be remembered as a president who allowed N. Korea to be a full-blown nuclear power which can directly threaten and casually push around U.S.. Since previous administrations share most of blame for letting this crisis fester and metastasize, this label would be unfair to him, but Dems will hang this around his neck and make it stick. Dems are eager to deal a blow to his leadership and make him less effective, painting him as another waffling leader. He has limited window of opportunity to act. Either he takes care of it this year or it may be out of his reach.