Washington: Pakistan's support for Haqqani network has increased through both facilitating additional sanctuary and providing strategic and operational guidance, a top US think tank has said.

In its report on Monday, the Institute for the Study of War has asserted that the network represents a strategic threat to the enduring stability of the Afghan state and US national security interests in the region.

"The Haqqani Network is the primary proxy force backed by elements of Pakistan's security establishment. Pakistan's support for the Haqqani Network has increased, through both facilitating additional sanctuary and providing strategic and operational guidance," the report "The Haqqani Network: A Strategic Threat" said.

Pak-based terrorist outfit the Haqqanis are currently Afghanistan's most capable and potent insurgent group, and they continue to maintain close operational and strategic ties with al Qaeda and their affiliates, it said.

These ties will likely deepen in the future, it noted.

Given the increasing strength of the Haqqani network, the report recommended the US must not abruptly shift the mission of its forces in Afghanistan from counter-insurgency to security force assistance.

"US forces cannot curtail or cease offensive operations in the areas South of Kabul in Regional Command East in 2012. The United States and its Afghan partners must dismantle the Haqqani Network's strongholds in Khost, Paktika, and Paktia and contain the organisation's expansion toward Kabul prior to a shift in mission. Failure to do so will present a strategic threat to US national security interests in Afghanistan," it said.

The Washington-based think tank said coalition and Afghan forces must conduct a sustained, well-resourced offensive against the Haqqani network inside of Afghanistan.

This campaign would likely require at least two adequately-resourced fighting seasons.

"Consequently, it is imperative that the US retains force levels at 68,000 troops after September 2012, rather than conducting a further drawdown. Without such a campaign, the Haqqani Network will be a dominant force inside of Afghanistan indefinitely, and the United States would fail to achieve its stated objective of preventing the return of al-Qaeda and affiliated groups to Afghanistan," it said.

The Haqqanis maintain considerable sanctuary and support nodes inside Pakistan's tribal areas, it said.

"From their safe havens in North Waziristan and Kurram Agencies in Pakistan, the Haqqanis project men and materiel to resource their terrorist campaign in Afghanistan's southeastern provinces of Khost, Paktika and Paktia onwards to the provinces surrounding Kabul," it said.