"We are not deploying nuclear armed land-based missiles outside of our national territory to other NPT nuclear weapon states," Sheinman said.
The official also said the US is not developing nuclear armed hypersonic glide vehicles.
The global conference brings countries together to review the NPT every five years. Under the NPT, the nuclear five - Russia, the United States, the United Kingdom, France, and China - agreed to never transfer nuclear weapons or share the technology with non-nuclear nations.
Despite its historic significance as a cornerstone of the global non-proliferation regime, however, the treaty has been criticized for failing to encourage nuclear-armed nations to give up their arsenals or to stop non-nuclear states from building an atomic bomb.