The treaty cannot come into force until it is ratified by the required 44 states which had nuclear research or power facilities when it was adopted in 1996. Only 33 have done so. The United States, the world's leading nuclear power, Colombia, Egypt, Indonesia, China, Iran, Israel and Vietnam are among the remaining 11 countries that have not ratified the Comprehensive Test Ban Treaty.

http://www.truthout.org/docs_2005/092405E.shtml