On the fourth observance of the day, Ban issued a statement saying the treaty to end nuclear weapon test explosions "remains a serious matter of unfinished business on the disarmament agenda."
"Although 20 years have passed since the Conference on Disarmament began negotiations on the Comprehensive Nuclear-Test-Ban Treaty, this treaty has still not entered into force," he said in a statement. "Today, 183 countries around the world have signed the CTBT and 159 have ratified it."
At least eight more countries must sign the CTBT in order to enforce the treaty.
Ban said the strong international response to North Korea's nuclear test earlier this year "demonstrated the commitment of the international community to uphold the global norm against nuclear tests."
"I once again urge all states to sign and ratify the CTBT without further delay. The eight remaining states whose ratifications are necessary for the treaty to enter into force have a special responsibility; none should wait for others to act first," he said. "In the meantime, all states should maintain or implement moratoria on nuclear explosions. I also encourage civil society, academia and others to continue to contribute their crucial advocacy."
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