The United States at this point of time is not in a position to certify that there is no link between the Pakistan's spy agency Inter-Services Intelligence and the dreaded Haqqani network, a senior top American official has said.

Responding to questions from agitated lawmakers about links between the ISI and the Haqqani network, Deputy Special Representative for Afghanistan and Pakistan Daniel Feldman said that at this point the US Government can't certify thatthere is no link between them.

"That's one of the certifications that we're working through right now and we don't have an answer for you at this point. But we are taking that certification, which I know you've been quite involved with very seriously, and trying to look at it as soberly as possible," Feltman said in response to a question from Congressman Michael McCaul.

"They (Haqqani network) are killing our soldiers, and the idea that the Pakistanis could be complicit and working with them -- which I personally believe is true -- is very troubling to policymakers like ourselves, and particularly when it comes to foreign aid. Can you -- could the Secretary (of State) certify today that the Pakistani government is in no way working with the Haqqani network?" MCcaul asked.

"We need to be in a position where in every engagement with the Pakistanis we can continue to show the need for increased cooperation on extremists, including among the Haqqani network, which pose a threat to both of us. And there's clearly more that could be done, but the way that we continue to try to get this done is through increased engagement," Feltman said.

"As the Secretary (of State, Hillary) Clinton said when she was there last, it's through issues like the financing networks, on intelligence sharing, on working with law enforcement personnel to deny safe havens. We raise this at every opportunity at every level in all of our engagements," Feltman said.

"I just think, again, when it comes to being able to certify whether or not Pakistan, ISI or government, at any level is working with Haqqani, it sounds like this is a work in progress within the administration in terms of whether or not they can certify that question," the Congressman said, asking again if the US is aware of any evidence that the

Pakistan and the ISI are co-operating and working together.

"There's a range of evidence and depending on the certification for the steps that they have taken countering extremism and terrorism, including on Taliban and including on Quetta Shura and less on the Haqqani network, but we continued efforts to try to encourage," Feltman said.

Congressman Gerald Connolly said that on a bipartisan basis, there is troubling evidence of lack of co-operation with the Pakistani Government on the issue of Haqqani network.

"I think in this Congress on a bipartisan basis there is very troubling evidence of the lack of cooperation with the Pakistani government on this matter, and the Haqqani network is a very dangerous, potent network that has been listed as terrorist," Connolly said.

"If we're going to have a partnership or collaboration with the Pakistani government, that's the least we can expect of them, and the idea that they actually harbor the Haqqani in Pakistan is extremely troubling. The fact that we make representations to the Pakistani government is not sufficient," an agitated Connolly said as he appeared to be dissatisfied with the remarks of the US official testifying before the committee.

"Our counterintelligence efforts are core to our shared interest here, and the Haqqani network is chief amongst them. We continue to -- there are key Haqqani targets who have  been killed in Pakistan over the last year, both through our own and shared efforts, and there are a range of other alternatives that we are taking to try to continue to target them," Feldman said in response to a question.

"There is convincing evidence that elements of the Pakistani government have protected the Haqqani network within the borders of Pakistan. What are we doing to change that?" Connolly asked.

"We are working jointly with the Pakistanis on targetting Haqqani very, very explicitly. We've targeted them through listings, specifically individually. We continue to work with the Pakistanis on ways that we can confront this, not only through military efforts but through a range of efforts that the civilian government, the intelligence channels and others can take," Feldman responded.

Not satisfied, Connolly asked: "Is it your testimony to this subcommittee that the Pakistani government and all of its elements, including the ISI, are in full cooperation with the United States in trying to suppress the Haqqani network as a terrorist organisation?"

The US continues to work with the Pakistanis very closely on all extremist threats posed to both the US and Pakistan, including the Haqqani network, Feltman answered.

Congressman McCaul asked about the remarks of the then Chairman of the Joint Chiefs of Staff, Admiral Mike Mullen, in which he had had alleged that the Haqqani network is  a veritable arm of the ISI.

"As Chairman Mullen said and he expressed the administration's view that continuing safe havens are extremely troubling and we have to see action taken against them. But he also emphasized in the exact same testimony that we need to continue to stay engaged to be able to do that. And he cautioned against signs of disengaging with Pakistan," Feltman said.