The general's report carries a direct call for extra troops
The US mission in Afghanistan will "likely result in failure" unless troops are increased within a year, the top general there has said in a report.
Gen Stanley McChrystal made his assessment in a confidential report obtained by the Washington Post.
He recently called for a revised military strategy in Afghanistan, suggesting the current one is failing.
More than 30,000 extra US troops have been sent to Afghanistan since May - almost doubling the US contingent.
The number of US troops in Afghanistan is already set to rise to 68,000 by the end of the year.
Paul Reynolds, BBC world affairs correspondent
Gen McChrystal has dared to use the F-word - "failure". He wants a super-surge of troops to try to avoid that. Reinforcements are already being sent, almost doubling US troops by the end of this year.
Now, the general wants perhaps tens of thousands more. Yet the request is in contrast to the stated goal of handing over operations more and more to the Afghan army.
With the situation so critical, how can that happen? Answer - it cannot for the time being. And will President Obama agree?
He is reluctant just to add to the numbers but without numbers, how can the US and its allies win? And will the Nato allies give more help? This must be doubtful.
Stark concerns have previously been expressed about the viability of the military mission in Afghanistan, but the BBC's Paul Reynolds says what is new about the general's warning is his outright use of the word "failure".
Gen McChrystal, who took over as military commander in May, is expected to make a separate request for tens of thousands of extra forces to be deployed.
He also says that training for Afghan forces needs to be speeded up - and that the growth of Afghan forces should also be accelerated.
A senior adviser to Afghan President Hamid Karzai said the government was not against more international troops being sent, though their success would depend on where they were sent.
But he agreed that domestic forces were crucial to the operation.
"Our official stance is that until our security forces are strengthened, both in terms of numbers and quality, there won't be a long-lasting peace in Afghanistan," Sebghatullah Sanjar told the BBC.
US President Barack Obama has recently said the right strategy for Afghanistan will have to be found before any fresh commitment of forces can be considered.
In his latest assessment, Gen McChrystal is quoted by the Washington Post newspaper as saying: "Failure to gain the initiative and reverse insurgent momentum in the near-term [next 12 months]... risks an outcome where defeating the insurgency is no longer possible."
He warns that "inadequate resources will likely result in failure".
"Additional resources are required," the general states in the summary of the report.
He says that failure to provide adequate resources "risks a longer conflict, greater casualties, higher overall costs, and ultimately, a critical loss of political support".
"Any of these risks, in turn, are likely to result in mission failure."
HAVE YOUR SAY
It can be a success if all parties develop a backbone coupled with a clearly defined goal
Rich P, Milwaukee, Wisconsin
But Gen McChrystal adds that the increase in troop numbers must come in the context of a revised military strategy in the country.
He has consistently called for a strategy which makes its top priority the protection of the Afghan people.
In the report Gen McChrystal also:
- Provides new details about the sophisticated nature of the Taliban insurgency
- Criticises Nato forces for focusing more on tackling insurgents than protecting Afghan civilians
- Censures the Afghan government for lack of action on widespread corruption
- Warns that Afghanistan's prisons have become a sanctuary for active insurgents
All of these factors, he claims, have led to a "crisis of confidence among Afghans" in the face of a resilient insurgency.
MCCHRYSTAL'S NEW STRATEGY
Focus on protecting civilians when fighting insurgents
Interact more closely with local populations
More troops needed for effective counter-insurgency
Better training for Afghan forces to operate independently
Government and NGOs to provide services after military action
More constructive engagement with Taliban fighters willing to talk
The increase in troop numbers would provide security for the Afghan people and create a space in which good governance can take root, Gen McChrystal argues.
In a blunt evaluation, he says that both the Afghan government and international forces face losing credibility among the Afghan population.
"Pre-occupied with protection of our own forces, we have operated in a manner that distances us - physically and psychologically - from the people we seek to protect," he says.
But 2009 has been the deadliest year for foreign troops in Afghanistan since the fall of the Taliban in 2001.
Italy is holding a day of mourning for six soldiers killed in a Kabul bomb attack last week. And the future of German troops in Afghanistan has become a central issue in Germany's election campaign.
The Washington Post says that the report has been presented to US Defence Secretary Robert Gates.
A recent opinion poll showed that a narrow majority of Americans now oppose the conflict.
Last week the chairman of the Joint Chiefs of Staff Adm Mike Mullen, told the US Senate Armed Services Committee that more troops might be required to tackle the mounting Taliban insurgency.
But President Obama later said there was "no immediate decision pending" on sending more troops to Afghanistan.
"You have to get the strategy right and then make the determination about resources," Mr Obama said.
The BBC's security correspondent Nick Childs says the timing of this leak, and the stark language contained in it, is certain to pile the pressure on the Obama administration, particularly when the president has just said he is not ready to make a final decision.
This is largely because the issue has become so politically charged in Washington, our correspondent says.
US MEDIA REACTION TO MCCHRYSTAL REPORT
It's worth remembering that while we're reading about the strategy review's details now, Obama read it weeks ago, and still told David Gregory [on Sunday] that he refuses to add troops until he's convinced that the strategy is correct.
Spencer Ackerman, at the Washington Independent,
points out that the president's recent statements have been made with full knowledge of Gen McChrystal's recommendations.
This is a way for McChrystal's voice - missing so far from the debate - to be heard loud and clear, making the case for counter-insurgency tactics and more troops to back them up.
The National Review's Rich Lowry
welcomes Gen McChrystal's contribution.
I would guess that this leak is an indication that some on the Obama team are dismayed at the White House's slow response and fear that this is an indication that President Obama is leaning towards rejecting the inevitable requests for additional US forces that this report tees up. By this logic, the leak is designed to force his hand and perhaps even to tie his hands.
Foreign Policy's Peter Feaver
suspects the leak come from inside the White House, not from Gen McChrystal's team.
What is evident by the McChrystal recommendation (and by the apparent need to leak its contents, stemming no doubt from frustration with the White House stall) is that there is good reason to be concerned that the president's failure to make a prompt decision may in and of itself impair our ability to succeed.
Commentary's Jennifer Rubin
fears that any delay in implementing Gen McChrystal's proposals could damage the US mission in Afghanistan.
Already, Republicans are warning that Obama had better follow the military's advice, or else. In fact, the president can afford to cross swords with the GOP troglodytes, but what he can't afford is to alienate his own Democratic party base, which has overwhelmingly rejected the war.
Robert Dreyfuss, of the Nation,
counsels Mr Obama to ignore Jennifer Rubin and her conservative colleagues.
What, exactly, does he propose to do with the additional troops? If the idea is to spread them out in some way (for troop training, insurgent fighting, population protection, etc.), his request should probably be viewed skeptically. But if he can propose some key operation or area where additional troops would represent a doubling or tripling of capacity and success might have an outsize effect on the entire conflict, then it might be worth trying.
Kevin Drum, blogging at Mother Jones,
advises liberals to approach Gen McChrystal's proposals with an open mind.
INTERNATIONAL TROOPS IN AFGHANISTAN
Note: Map shows only Isaf troops - the US contributes additional forces
This is a full list of troop contributing nations to the International Security Assistance Force, Isaf: Albania, Australia, Austria, Azerbaijan, Belgium, Bosnia Herzegovina, Bulgaria, Canada, Croatia, Czech Rep, Denmark, Estonia, Finland, France, Georgia, Germany, Greece, Hungary, Iceland, Ireland, Italy, Jordan, Latvia, Lithuania, Luxembourg, Netherlands, New Zealand, Norway, Poland, Portugal, Romania, Singapore, Slovakia, Slovenia, Spain, Sweden, Former Yugoslav Republic of Macedonia, Turkey, Ukraine, UAE, UK, US