UN Secretary-General Ban Ki-moon has called on all countries to work to bring the entry into force of the Comprehensive Nuclear Test Ban Treaty (CTBT) as soon as possible.Open for signature in 1996, the legally binding CTBT is a multilateral treaty by which states agree to ban all nuclear explosions, for both civilian and military purposes, Xinhua news agency reported.In a message to the International Day against Nuclear Tests, Ban noted that since its adoption 20 years ago, the CTBT has yet to enter into force.Ban said a prohibition on all nuclear testing will boost momentum for other disarmament measures and it will build confidence for other regional security measures, including a Middle East zone free of nuclear weapons and all other weapons of mass destruction.The UN General Assembly declared August 29 the International Day against Nuclear Tests in 2009, calling for increasing awareness about the effects of nuclear weapon test explosions and the need for their cessation as one of the means to achieve the goal of a nuclear-weapon-free world.