The State Department spokesperson Kirby said Kerry called up Sharif last week and he is believing that Islamabad "is serious about this particular incident, serious about investigating it." Pakistan is taking serious steps to apprehend the conspirators behind the terrorist strike at the Pathankot Air Force base, the United States said.

“We do not talk much in detail about the diplomatic conversations. He came away believing that the Pakistani government is serious about this particular incident, serious about investigating it, serious about trying to work with partners in the region, Afghanistan specifically,” a senior State Department official said, referring to the conversation between Mr. Kerry and Mr. Sharif.

The official said: “I am not going to define it as a change in tone. I think, we all recognize that more can be done, including by Pakistan. But that does not mean that we would not keep working at it.”

“I don’t have any additional detail, we note and we’re encouraged by the fact that the Pakistani government condemned the attack and said that they would investigate. Our expectation is that the investigation will be thorough and complete and as transparent as possible. But in terms of its progress and where they are, you’d have to talk to Pakistani authorities about it,” Mr. Kirby said.

Pakistan on Monday submitted to India its initial findings of the investigation being conducted on alleged Pakistani links to the Pathankot terror attack, media reports. "The intelligence agencies have picked up some suspects from Bahawalpur on the leads provided by India in Pathankot airbase attack and shifted them to undisclosed location for interrogation," Pakistani news channel ARY News reported.

By Premji