Friday sees the end of a visit during which Karzai and President Barack Obama made a public show of unity in the fight against the Taliban and Al-Qaeda.
But analyst Phyllis Bennis at the Institute of Policy Studies in Washington believes that there are disagreements behind the façade.
“The main point – and I don’t know if it’s been resolved – is a significant strategic difference on the question of negotiations and reconciliation,” she told RFI.
“There are very different views between President Karzai and the Obama administration. It’s essentially on the question of who do we negotiate with, when do we negotiate and what is up for grabs.”
Both Washington and Kabul agree that negotiations should take place, says Bennis.
“But for the US the view is, we can’t talk to them now, we have to kill more first … which inevitably means killing more civilians.”
Karzai has frequently criticised foreign troops for the level of civilian casualties caused by their operations.
On Friday, hundreds of people demonstrated in eastern Afghanistan, accusing Nato forces of killing a dozen civilians during an overnight raid targeting Taliban militants.
The commander of US and Nato troops in Afghanistan, General Stanley McChrystal, on Thursday said there is still no clear winner in the war.
“In the last year, we've made a lot of progress," McChrystal told PBS television. "I think I'd be prepared to say nobody is winning at this point. Where the insurgents, I think, felt that they had momentum a year ago, felt that they were making clear progress - I think that's stopped."
After winning the town of Marjah, US and Nato planners are pinning their hopes on an offensive on the key southern city of Kandahar and villages around it.
McChrystal said that its effectiveness will not be clear until the end of the year.
“Ninety-five per cent said that more men have joined the Taliban this year than than before and, crucially, 61 per cent said that they feel more negative about the occupying … than they did before the offensive in Marjah than they did before,” she says.
“The war is going very badly for the US and it’s going to get worse,” Bennis concludes.