WASHINGTON  - The United States is pushing Islamabad to address the issue of prevalence of Pakistan-manufactured improvised explosive devices (IEDs) in Afghanistan that continues to be a major point of friction between the two countries.

US Defence Secretary Leon Panetta told lawmakers on Tuesday that the IED was the major reason of casualties of American soldiers in Afghanistan and that these explosives were manufactured in Pakistan, adding that in some ways, the IED issue was related to the terrorists’ safe havens.

Testifying before the Senate Armed Services Committee, Panetta said, “The supplies of IEDs continue to come from Pakistan and this is an area where action needs to be taken to be effective at trying to cut back on these.”

“We have made very clear to them (Pakistan) that, where these threats emanate from, we have identified locations. We’ve directed them to specific sites. We have urged them to take steps,” Panetta added.

“In some cases, they have. In some cases, they wind up there too late. But we’re continuing to impress upon them that they have got to be part of the answer to dealing with this issue,” the defence secretary said in response to a question from a senator. Joint Chiefs of Staff Chairman General Martin Dempsey noted that the relations with Pakistan had been somewhat challenged, but said, “They’re improving. And this is one of the points of friction between us that we have to get at.”

On the possible deal to release Taliban prisoners, Panetta said he would not approve the transfer of any Taliban inmates held at the US-run prison in Guantanamo Bay unless he was sure the detainees would not return to the battlefield.

President Barack Obama’s administration has confirmed tentative discussions with the Taliban on a potential transfer of five inmates from Guantanamo Bay. But Panetta struck a cautious tone at the Senate hearing, saying he was legally bound to ensure the release of an inmate would not pose a security threat.

“Absolutely, no decisions have been made along this line,” he stressed, adding, “I can tell you this, that based on the law that’s passed by the Congress, I have to certify that anybody who leaves Guantanamo cannot wind up going back to the enemy.”

“And I’ve got to be convinced that those kinds of protections are in place before I certify that anything like that happens.” General Martin Dempsey seconded Panetta’s views on the prisoner deal and said he had concerns about the security risks posed by transferring the detainees. However, he said that he supported efforts at reconciling with the insurgency after 10 years of war.

Speculation has swirled over initial US talks with the Taliban, with officials saying five Taliban militants might be transferred to Qatar as a confidence-building measure, possibly in exchange for the insurgency renouncing violence in a de facto break with Al-Qaeda extremists.

Republican lawmakers have voiced dismay over the potential deal, but analysts say Obama will almost certainly avoid taking such a politically-charged step ahead of the US presidential elections in November.