The UN has called for a moratorium on all nuclear tests before the Comprehensive Nuclear Test Ban Treaty (CTBT) comes into force,

Secretary General Ban Ki-moon has called on all countries to impose a moratorium on all nuclear tests, his special representative Miroslav Jenca told an international conference on nuclear disarmament in the Kazakh capital of Astana Thursday.

Earlier this month, Ban set the target year for CTBT's entry into force for 2012.

Russia joined the call. "It is important to provide a moratorium on nuclear tests before the treaty comes into force," Russian Ambassador to Kazakhstan Mikhail Bocharnikov said.

The CTBT, which was opened for signature in 1996, has been signed by 165 countries so far. But only 91 countries, including Russia, Britain and France, have ratified it.

The treaty will not come into force until the 44 most nuclear advanced countries ratify it. So far, only 31 have done so. India, Pakistan and North Korea have not even signed the document.