"With regards to the Pakistani intelligence services, I think that's been historically an issue in that country.

There are signs that it remains so. And we, our collect – our two governments are working to deal with those problems," said Geoff Morrel, Pentagon press secretary.

The Pentagon also said a "very, very small numbers of US special forces are operating in a training capacity in Pakistan, not out on joint missions, but on a fixed site, training Pakistani forces, at the invitation of the Pakistani government."

The US was particularly pleased to see that Pakistan is involved in operations in the federally administered tribal areas (FATA) but said "robust efforts" are needed to tackle the problem.

"We have seen and continue to see Pakistani military operations in the FATA, and we are pleased to see that. But, this needs to be a concerted and consistent effort to go after the militants to prevent them from either creating training grounds and safe havens within Pakistan or going into Afghanistan and causing trouble there," the senior Pentagon official said.

"So there clearly are increased military operations. We've seen that. We are pleased by it. We need to continue to see it and we need to see probably even more robust efforts on the Pakistan's part," he added.