North Korea conducted the nuclear test on Friday and said it had mastered the ability to mount a warhead on a ballistic missile, ratcheting up a threat that its rivals and the United Nations have been powerless to contain.
"North Korea is seeking to perfect its nuclear weapons and their delivery vehicles so they can hold the region and the world hostage under threat of nuclear strike," U.S. Ambassador Samantha Power told reporters ahead of the council meeting.
"We will take additional significant steps, including new sanctions to demonstrate to North Korea that there are consequences to its unlawful and dangerous actions," Power said.
North Korea has been under U.N. sanctions since 2006. In March, the Security Council tightened sanctions to further isolate the impoverished country after its fourth nuclear test in January and a long-range rocket launch in February.
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"Weakness is simply not an option, North Korea will have to bear the consequences of its actions and provocations," French U.N. Ambassador Francois Delattre told reporters. "France calls for the adoption as soon as possible of a new resolution."
Russian U.N. Ambassador Vitaly Churkin told reporters: "I think we should condemn it first of all and then we will see what we can do."
Pyongyang has also carried out a string of ballistic missile tests this year in defiance of U.N. sanctions, which have all been condemned by the Security Council.
In the unanimously adopted March resolution, the council expressed "its determination to take further significant measures in the event of a further DPRK (North Korea) nuclear test or launch."
British U.N. Ambassador Matthew Rycroft said there were a series of steps the Security Council could take to respond to Friday's nuclear test and that Britain would like to see a combination of those steps imposed.
"First of all there must be full implementation of the existing sanctions, secondly there could be additional names added to the existing sanctions regime ... and thirdly there could be a tightening up and a strengthening of the sanctions regime," Rycroft told reporters ahead of the council meeting.
United Nations Secretary-General Ban Ki-moon condemned North Korea's nuclear test on Friday as a "brazen breach" of U.N. Security Council resolutions.
"I count on the Security Council to remain united and take appropriate action. We must urgently break this accelerating spiral of escalation," he told reporters.
