WASHINGTON: The reconciliation talks with the Taliban will succeed if Pakistan agrees to play a constructive role in those talks, says Senator Carl Levin, chairman of the US Senate Armed Services Committee.

At a Senate hearing on Tuesday afternoon, US lawmakers and military officials reviewed Pakistan's role in the US-led peace efforts in Afghanistan, focusing on how tensions between Islamabad and Washington could affect those efforts.

"The progress of reconciliation talks with the Taliban," the senator observed, would be determined by various factors, including "whether Pakistan chooses to play a constructive role in those talks".

Another important requirement for bringing peace to Afghanistan was the elimination of the threat from insurgent safe havens in Pakistan, Senator Levin added.Senator John McCain, the ranking Republican member of the committee, observed that the US relationship with Pakistan "remains fraught by a series of setbacks and a lack of trust, largely arising from the fact that the country's intelligence service continues to support terrorist groups such as the Haqqani network, that are killing Americans".

Admiral William McRaven, commander of US Special Operations Command, told Senator Kelly Ayotte, a New Hampshire Republican, that if Al Qaeda leader Ayman al-Zawahiri was caught in Pakistan the decision to keep him there or bring him to the United States would be made in consultation with the Pakistani government.

Senator Jim Webb, a Virginia Democrat, pointed that the US had not succeeded in winning over Pakistan's support against Iran as Islamabad still "calls them their most important friend".

Senator Richard Blumenthal, a Connecticut Democrat, raised the issue of IEDs, claiming that Pakistan remained the main source of the materials used for making the devices.

"It has been an area of frustration. It has been a serious topic of dialogue with us," Gen James Mattis, commander of US Central Command, told the panel.

The Pakistanis, however, had now passed the laws that would enable them to make arrests that they could not make before. They've also put together their counter-IED strategy in the last few months, the general said.

"I need to get back into Pakistan and talk with them more about it. There is some reason for more optimism today than if I was testifying last year," Gen Mattis said.

"Can you talk about where we are in negotiating reopening of (Nato supply routes) and how important that will be?" asked Senator Jeanne Shaheen, a New Hampshire Democrat.

"It is important to us. We have proven that we can sustain the campaign through the Northern Distribution Network and through what we call our multimodal, which is basically part by air, part by sea, re-supply of our effort there," Gen Mattis replied.

"However, the withdrawal out of Afghanistan we do need the ground lines of communication through Pakistan. As far as the status of that discussion, I will fly to Pakistan here in about ten days and we'll reopen the discussion."

Gen Mattis said he believed the parliamentary process launched to determine a new relationship with the United States would be over by that point and the Pakistani "military will be able to engage with us".