"It would be a tool to prevent the emission of a huge volume of green house gas as this emerging country of a billion people continues its rapid growth," the Japanese top official said.

Machimura was quoted by the Kyodo news agency as saying that the safeguards agreement India has reached with the International Atomic Energy Agency would ensure inspection of India's nuclear facilities and increase transparency of the country's nuclear activities.

The top Japanese official said despite his country's backing  of the civil nuclear deal at the key NSG meet in Vienna [Images], Tokyo still had concerns. "We would continue to assert that India should join the comprehensive test ban treaty," Machimura said.