However, India has not signed the CTBT, or the Nuclear Non-Proliferation Treaty, claiming the discriminatory nature of the treaty that allows the five declared nuclear countries of the world to keep their nuclear arsenal and develop it using computer simulation testing. Prior to its nuclear testing, India had pressed for a comprehensive destruction of nuclear weapons by all countries of the world in a time-bound frame. This was not favoured by the United States and by certain other countries. Presently, India has declared its policy of "no-first use of nuclear weapons" and the maintenance of a "credible nuclear deterrence". The USA, under President George W. Bush has also lifted most of its sanctions on India and has resumed military co-operation. Relations with USA have considerably improved in the recent years, with the two countries taking part in joint naval exercises off the coast of India and joint air exercises both in India as well as in the United States.