Amidst a new phase of bonhomie of peace between India and Pakistan, a top US intelligence official has said that it is very difficult to achieve peace between the two neighbours because of a lot of countervailing factors which could be explained only in a classified session.

"There have been some encouraging breaks here in the context of dialogue between the two countries, and I know from having traveled and dialogued with, certainly, the Indians are very - would be very interested as well in relaxing tensions," Director of National Intelligence James Clapper said.

"There are long-standing fundamental issues there that I think will be hard to overcome. Obviously, if they did reach some agreement it would be huge. But there are lots of countervailing factors, I think, that best left for discussion in closed session -- that I think are going to make that difficult," Clapper said.

He was responding to question from Senator Jeanne Shaheen on India-Pakistan relations during a Congressional hearing by the Senate Armed Services Committee.

"Pakistan's relations with India play a role in their defence plans and operations. There's been some small good news in terms of the potential for a thaw in that relationship in the last year or so.    Can you talk about how you assess the potential for improved ties between the two countries and how that might affect stability in that region?" the Senator asked.

"Well, obviously, from Pakistan's standpoint they view India as an existential threat," the Clapper said.

In his testimony before Senate Armed Services Committee, Ronald L Burgess, Director, Defence Intelligence Agency, said that Pakistan views India as its greatest threat, but Islamabad has engaged in confidence building talks with New Delhi that seeks an expansion of economic ties.

"The military situation is calm, but a major terrorist attack, especially if linked to Pakistan, would jeopardize continued progress. New Delhi and Islamabad are expected to hold talks on confidence building measures in 2012. Sustained momentum on these issues may enable discussions on more contentious issues over time," he said.