Was an agreement not to provide nuclear weapons to other nations and to encourage general disarmament and destruction of existing nuclear weapons?

Yes, such an agreement exists in the form of the Treaty on the Non-Proliferation of Nuclear Weapons (NPT), which was opened for signature in 1968. The treaty aims to prevent the spread of nuclear weapons, promote peaceful uses of nuclear energy, and encourage disarmament. It establishes a framework for nuclear-armed states to work towards disarmament while non-nuclear states commit not to acquire nuclear weapons. The NPT has been instrumental in international efforts to control nuclear proliferation and promote global security.