The Bush administration visualises a "qualitative change" in US-India relations in the wake of the civilian nuclear agreement between the two countries.

"Well, it (the agreement) opens up quite obvious possibilities in the nuclear energy sector. But it is also certainly symbolic of a new chapter in US-India relations," State Department spokesman Sean McCormack said on Thursday.

"I think it certainly signifies a qualitative change in our relationship that has been building for quite some time, but there were certain obstacles for it to actually proceed to the next stage. And one of these was this issue of India's nuclear programme and how it related to the rest of the world, and then other issues," McCormack said.

"So yes, we think that it is quite important. It was quite an important moment in US-India relations and there's more to be done to broaden and deepen the relationship," he said adding, "I think you'll probably see more activity in that regard from the secretary as well as others in the administration in the months ahead."

"There's still work to do, mind you, in terms of negotiating some of the agreements; 123 agreement and then India also has to negotiate a separate agreement with the IAEA (International Atomic Energy Agency), and then the Nuclear Suppliers Group (NSG) has to act. So, there are some other things related to this issue that have to happen before it's really completed, but I think it is also a demonstration of trust and confidence and willingness to bargain on this issue that certainly opens the door to a different kind of relationship," the spokesman said.

Asked about the rationale behind the US opposition to Iran's nuclear programme when it was allowing concessions to India in the same field, McCormack said, "I think it's self-evident. I mean, I think there's just no comparison in terms of Indian behaviour and responsibility with respect to its nuclear programme, and what the Iranians are doing. It's an easy answer."