The study by Rand Corporation, funded by the US Department of Defence, finds that Pakistan's Inter-Services Intelligence Directorate and Frontier Corps have failed to root out Afghan insurgent groups based in Pakistan and, in some cases, individuals from these Pakistani organisations have provided direct assistance to such groups as the Taliban and Haqqani network.

"Every successful insurgency in Afghanistan since 1979 enjoyed safe haven in neighbouring countries, and the current insurgency is no different," said report author Seth Jones, a senior political scientist at Rand.

"Right now, the Taliban and other groups are getting help from individuals within Pakistan's government, and until that ends, the region's long-term security is in jeopardy," the study titled "Counter-insurgency in Afghanistan," says.

It noted that insurgent groups have successfully established a sanctuary in Pakistan. The study finds that the insurgent groups found refuge in Pakistan's Federally Administered Tribal Areas, North West Frontier Province and Balochistan.

They regularly ship weapons, ammunition and supplies into Afghanistan from Pakistan, and a number of suicide bombers have come from Afghan refugee camps based in Pakistan.

The insurgent groups have acquired external support and assistance from the global 'jihadist' network, including groups with a strong foothold in Pakistan, such as al-Qaeda.

This assistance enables Afghan insurgent groups to adapt their tactics, techniques, and procedures to become, in effect, learning organisations, the study says.

It says that the outcome of the insurgency in Afghanistan and neighbouring Pakistan is of intrinsic importance to the United States.

"Solving this problem will require a difficult diplomatic feat: convincing Pakistan's government to undermine the sanctuary on its soil," Jones said in a press release.

Pointing to the growing list of terrorist attacks and foiled plots in the US, UK, Germany, Denmark, and Spain, US intelligence agencies have identified terrorist plots stemming from the Afghanistan-Pakistan border region as perhaps the single most important threat to America's security.

The North Atlantic Treaty Organisation's (NATO) reputation is also at stake over its first ever involvement in ground combat and its credibility would be severely tarnished if it failed to stabilise Afghanistan, it said.

Interestingly, the study found that governments with high levels of popular support prevailed in two-thirds of all completed insurgencies, but they won less than a third of the insurgencies when they had medium or low levels of support.

In addition, insurgent groups that enjoyed support from external states won more than 50 per cent of the time, those with support from non-state actors and diaspora groups won just over 30 per cent of the time, and those with no external support won only 17 per cent of the time.

Moreover, sanctuary in neighbouring states was particularly important for insurgent groups, the study says.

The findings of the study have significant implications for US counter-insurgency efforts in Afghanistan. "They suggest that declining support for the government and outside support for insurgents have directly contributed to the deteriorating security environment," it said.

Eliminating the Pakistan sanctuary bases is one of the study's three key recommendations. It also emphasises the need for the US and its allies to help build the Afghan security forces, particularly the police, and to improve the quality of local governments, especially in Afghanistan's rural regions.

The report finds that Afghanistan's national police force is in disarray, incompetent and almost uniformly corrupt, and its members are often loyal to local commanders at the expense of the country's central government.