The general's report will not carry a direct call for extra troops
A top US general in Afghanistan has called for a revised military strategy, suggesting the current one is failing.
In a strategic assessment, Gen Stanley McChrystal said that, while the Afghan situation was serious, success was still achievable.
The report has not yet been published, but sources say Gen McChrystal sees protecting the Afghan people against the Taliban as the top priority.
The report does not carry a direct call for increasing troop numbers.
"The situation in Afghanistan is serious, but success is achievable and demands a revised implementation strategy, commitment and resolve, and increased unity of effort," Gen McChrystal said in the assessment.
Copies of the document have been sent to Nato Secretary General Anders Fogh Rasmussen and US Defence Secretary Robert Gates.
Mr Gates said that although he had not yet seen the report he expected it to show that there were "challenges that remain before us... and areas where we can do better" in Afghanistan.
"There is no question that we have a tough fight ahead of us, but by the same token a lot of positive things have been happening," Mr Gates said.
He highlighted the increase in US and other troops and Afghanistan's recent presidential election, despite continuing violence in the country, but warned that casualties were going to rise as troops tackled the Taliban.
The report came as further results from last week's presidential election were released, with ballots now counted from almost 48% of polling stations.
President Hamid Karzai is leading so far, with 45.8% of the votes counted.
The independent Electoral Complaints Commission says that of more than 2,100 allegations of wrongdoing during voting and vote-counting, 618 have been deemed serious enough to affect the election's outcome, if proven.
Crisis of confidence
Gen McChrystal's blunt assessment will say that the Afghan people are undergoing a crisis of confidence because the war against the Taliban has not made their lives better, says BBC North America editor Mark Mardell.
The general says the aim should be for Afghan forces to take the lead - but their army will not be ready to do that for three years and it will take much longer for the police.
And he will warn that villages have to be taken from the Taliban and held, not merely taken.
Responding to Gen McChrystal's review, Afghanistan's deputy minister of rural rehabilitation, Wais Barmak, said Afghans should have been consulted about military strategy from the start.
"We would have had better achievements, better results, if the Afghans were consulted right from the beginning," he told the BBC's Newshour programme.
He said the government and development agencies should provide services for the people in the aftermath of the military operation.
"That is one way to engage with the people on the ground and re-establish the trust and confidence of the people in their government."
Gen McChrystal also wants more engagement with the Taliban fighters and believes that 60% of the problem would go away if they could be found jobs.
More than 30,000 extra US troops have been sent to Afghanistan since President Barack Obama ordered reinforcements in May - almost doubling his country's contingent and increasing the Western total to about 100,000.
This report does not mention increasing troop numbers - that is for another report later in the year - but the hints are all there, our correspondent says.
But when Gen McChrystal's report lands on Mr Obama's desk he will have to ponder the implications of increasing a commitment to a conflict which opinion polls suggest is losing support among the American people.
The latest Washington Post-ABC news poll suggests that only 49% of Americans now think the fight in Afghanistan is worth it.
In a recent BBC interview, Gen McChrystal said that he was changing the whole approach to the conflict in Afghanistan - from what he described as a focus on "body count", to enabling the Afghans to get rid of the Taliban themselves.
On Saturday, British Prime Minister Gordon Brown promised more support for UK troops in Afghanistan, during a surprise visit to the country.
During the visit he met Gen McChrystal. Correspondents say the pair discussed the need to speed up the pace of training of Afghan troops.
The British Ministry of Defence said it would look closely at any recommendations from Gen McChrystal.
"The UK conducted a review of policy earlier this year and the prime minister set out a new strategy on Afghanistan and Pakistan on 29 April.
"General McChrystal's work will be an important input to further planning, and we will work closely with him and our Nato partners moving forward," an MoD spokesman added.
• An earlier version of this article suggested that General McChrystal's report was expected to liken the American military in Afghanistan to a bull charging at a matador [the Taliban] - slightly weakened each time it is "cut".
In fact this remark was part of a more general commentary on US counterinsurgency policy, made by Gen McChrystal in his Counterinsurgency Guidance to units in the field, issued last week.