An assertive China and the violent extremism poses greatest challenge to the Asia Pacific region in the long term, but North Korea is the most immediate and pressing challenge, a top American commander has said. “The biggest challenge is an aggressive and assertive China. But the most immediate challenge today is and remains North Korea,” Commander of the US Pacific Command or PACOM Admiral Harry Harris said. “The other issue that faces all the nations in the (Asia Pacific) region, including the US, and we’re actively engaged in this, is ISIS and kind of violent extremist activity, terrorism really,” Harris said.