PAKISTAN could collapse within months, one of the more influential counter-insurgency voices in Washington says.
The warning comes as the US scrambles to redeploy its military forces and diplomats in an attempt to stem rising violence and anarchy in Afghanistan and Pakistan.
"We have to face the fact that if Pakistan collapses it will dwarf anything we have seen so far in whatever we're calling the war on terror now," said David Kilcullen, a former Australian Army officer who was a specialist adviser for the Bush administration and is now a consultant to the Obama White House.
"You just can't say that you're not going to worry about al-Qaeda taking control of Pakistan and its nukes," he said.
As the US implements a new strategy in Central Asia so comprehensive that some analysts now dub the cross-border conflict "Obama's war", Dr Kilcullen said time was running out for international efforts to pull both countries back from the brink.
When he unveiled his new "Afpak" policy in Washington last month, the US President, Barack Obama, warned that while al-Qaeda would fill the vacuum if Afghanistan collapsed, the terrorist group was already rooted in Pakistan, plotting more attacks on the US.
"The safety of people round the world is at stake," he said.
Laying out the scale of the challenges facing the US in Iraq, Afghanistan and Pakistan, Dr Kilcullen put the two countries invaded by US-led forces after the September 11 attacks on the US on a par - each had a population of more than 30 million.
"But Pakistan has 173 million people and 100 nuclear weapons, an army which is bigger than the American army, and the headquarters of al-Qaeda sitting in two-thirds of the country which the Government does not control," he told the Herald .
Added to that, the Pakistani security establishment ignored direction from the elected Government in Islamabad as waves of extremist violence spread across the whole country - not only in the tribal wilds of the Afghan border region.
Cautioning against an excessive focus by Western governments on Afghanistan at the expense of Pakistan, Dr Kilcullen said that "the Kabul tail was wagging the dog". Comparing the challenges in the two, he said Afghanistan was a campaign to defend a reconstruction program. "It's not really about al-Qaeda. Afghanistan doesn't worry me. Pakistan does."
But he was hesitant about the level of resources for, and the likely impact of, Washington's new drive to emulate an Iraq-style "surge" by sending an extra 21,000 troops to Afghanistan.
"In Iraq, five brigades went into the centre of Baghdad in five months. In Afghanistan, it will be two combat brigades [across the country] in 12 months. That will have much less of a punch effect than we had in Iraq.
"We can muddle through in Afghanistan. It is problematic and difficult but we know what to do. What we don't know is if we have the time or if we can afford the cost of what needs to be done."
Dr Kilcullen said a fault line had developed in the West's grasp of circumstances on each side of the Durand Line, the disputed border between Afghanistan and Pakistan.
"In Afghanistan, it's easy to understand, difficult to execute. But in Pakistan, it is very difficult to understand and it's extremely difficult for us to generate any leverage, because Pakistan does not want our help.
"In a sense there is no Pakistan - no single set of opinion. Pakistan has a military and intelligence establishment that refuses to follow the directions of its civilian leadership. They have a tradition of using regional extremist groups as unconventional counterweights against India's regional influence."
In the absence of a regional diplomatic initiative to build economic and trade confidences before tackling the security issue, the implication, Dr Kilcullen said, was that India alone could not give Pakistan the security guarantees Islamabad required.
The special US envoy Richard Holbrooke has been charged with brokering a regional compact by reaching out to Iran, Russia and China, and Dr Kilcullen said: "This is exactly what he's good at and it could work.
"But will it? It requires regional architecture to give the Pakistani security establishment a sense of security which might make them stop supporting the Taliban," he said.
"The best case scenario is that the US can deal with Afghanistan, with President Obama giving leadership while the extra American troops succeed on the ground - at the same time as Mr Holbrooke seeks a regional security deal," he said. The worst case was that Washington would fail to stabilise Afghanistan, Pakistan would collapse and al-Qaeda would end up running what he called 'Talibanistan.'
"This is not acceptable. You can't have al-Qaeda in control of Pakistan's missiles," he said.
"It's too early to tell which way it will go. We'll start to know about July. That's the peak fighting season ... and a month from the Afghan presidential election."