WASHINGTON - Welcoming Pakistan’s commitment to combat "all terrorists", the United States has described Prime Minister Nawaz Sharif’s commitment to take action against Lashkar-e-Taiba (LeT) as a very significant development.

“This is indeed something very new," a senior Obama administration said, referring to the joint statement issued after Thursday's talks between PM Sharif and President Barack Obama in which the Pakistani leader spoke of his government's resolve to take "effective action" against UN-designated terrorist individuals and entities, including LeT and its affiliates, as per its international commitments and obligations under UN Security Council resolutions.

The administration official, who was speaking on condition of anonymity, said it was "very significant that the President (Barack Obama) and the prime minister discussed Pakistan’s efforts to take action against Lashkar e-Taiba and its affiliates as part of these commitments.

"So this is something new, and I think it demonstrates a recognition by Pakistan of the threat these terrorist groups pose to Pakistan and other countries in the region as well as to the United States and other peace-loving countries," the official said on Friday.

"We have been discussing our concerns about terrorism of the region with Pakistan, really going back before 9/11. But certainly since the tragic attack on September 11 against the United States, these discussions have continued and had counterterrorism cooperation with Pakistan over the years. But I think we had a significant shift with Pakistan after the tragic attack against the school in Peshawar in December 2014 in which 140 people were killed.”

Responding to a question, the official said the Obama administration has not notified to the Congress about the proposed sale of eight F-16 fighter jets to Pakistan.

"I can confirm - just state that we have not notified Congress of any new sale," the official said, in response to questions about a media report in this regard.

"The US has sold F-16s to Pakistan in the past. We understand that Pakistan uses these very actively in its military operation against militants and terrorist groups operating in western Pakistan. This is something that Pakistan government briefs us on and we are very pleased that these aircraft that were supplied by the US government can be so effective in countering militants," the official said.

Noting that the US has longstanding security cooperation with Pakistan, the official said it is in each of the countries interest.

"We do think, it is in region’s interest as well. Pakistan has taken very determined actions in the last several years against militants operating on its territory. These are militants and terrorists that not only threaten Pakistan, but they threaten other countries in the region and they threaten our interest as well," the official added.

The official dismissed reports about a civil nuclear deal, saying Pakistan has made clear its interest in civilian nuclear cooperation and has called this a socio-economic imperative because of its energy shortfalls. "But we’ve not entered into negotiations on a 123 (Indo-US style) agreement with Pakistan, nor are we seeking an exception for Pakistan within the Nuclear Suppliers Group in order to facilitate civil nuclear exports."

The official said nuclear security was discussed at the Obama-Sharif meeting. "And as I would say more generally, the US urges all nuclear-capable states, including Pakistan, to exercise restraint regarding nuclear weapons and missile capabilities," the official said.

"In particular, we’ve discussed efforts to strengthen safety and security measures for Pakistan and continue to hold regular discussions between Pakistan and the United States on these issues. So we discuss it now, but this was part of an ongoing process where we discuss these issues with Pakistan and express our concerns to them."

The official also ruled out any US role in the India-Pakistan peace process unless both the countries ask for it.

"(During the meeting) we affirmed the US commitment that we would be engaged only if this is something that India and Pakistan would like. This is not any change in any policy of the United States."

"This has been a reiteration of the continued policy of the United States for both countries to work out these issues bilaterally and of course we and other countries would be willing to provide facilitating and other supporting role if India and Pakistan together ask for," said the official.

The official, requesting anonymity, did acknowledge that it has received set of dossiers from Pakistan on alleged Indian activities in parts of Pakistan.

"In the meeting with Secretary of State, John Kerry (on Wednesday) Prime Minister did share, hand over written material relating to certain concerns that Pakistan has about security in the region," the official said.

"As we have long said, and as the secretary underscored, the best way to resolve issues is through direct dialogue between the two neighbors. We stand ready to support such dialogue in any way we can. We have just received these dossiers. We have not reviewed them and we do not have any comment on the contents at this point," the official said.

"A dialogue between India and Pakistan, the parameters of which, it is for India and Pakistan to work out. It is not the policy of the US to try to influence or try to set terms or otherwise even make recommendations for how that dialogue should take place. This is our policy for many years. That policy of the US has not changed," said the official.

"The United States has very important relations with India and Pakistan," the official said. "They stand on their own; they’re not zero-sum. The United States has global interest and it has interest in the peace and stability of the region, which I think is something that President Obama indicated the United States is committed to with his decision last week to authorise our military forces to remain in Afghanistan, to remain in the region, beyond 2016."

About PM Sharif's proposal for a mechanism to deal with ceasefire violations along the Line of Control in the disputed Kashmir region, the official said, "Pakistan has often made requests for the United States to be engaged in this, but President Obama reaffirmed the US commitment that we would be engaged only if this is something that India and Pakistan would want."