The US Defence Secretary Donald Rumsfeld has played down hopes of an early capture of Osama Bin Laden.
Both Mr Rumsfeld and President Karzai said security had improved
Speaking after talks with the Afghan President Hamid Karzai, Mr Rumsfeld said he has no idea when the al-Qaeda leader would be captured or killed.
Mr Karzai said that the Taleban were now defeated and that most violence in Afghanistan was caused by criminals.
He was speaking the day after five Afghan aid workers were killed and two wounded in an ambush near Kabul.
Brought to justice
"I don't believe it is closer or farther at any given moment," Mr Rumsfeld told reporters about the prospects of catching Osama Bin Laden.
"The intent is there and I suspect that we will find that it is accomplished at some point in the future," he said, "but I would not have any idea when."
His comments follow a prediction last month by the American commander of coalition forces in Afghanistan, who said he expected Osama Bin Laden would be brought to justice by the end of this year.
Lieutenant-General David Barno said that the "sands in the hourglass" of all of the al-Qaeda senior leadership was running out.
Mr Rumsfeld, on his sixth visit to Afghanistan, told journalists that he had no indication that the Taleban posed a military threat.
Both he and President Karzai insisted the security situation was improving.
"We do not see a resurgence of the Taleban," the president said, "the Taleban as a movement does not exist any more."
Mr Rumsfeld said that the Taleban did not pose a military threat
However, correspondents in Afghanistan say that violence continues across the country.
On Wednesday evening, five Afghans working for a non-governmental organisation were killed, the third such attack in two weeks.
More than 100 people have died in such attacks this year, many of which are believed to have been carried out by Taleban militants.
News of the deaths came as Mr Rumsfeld arrived in the southern Afghan city of Kandahar.
There he saluted a graduating class of 48 Afghan policemen trained at the headquarters of a new civilian-military Provincial Reconstruction Team (PRT).
The PRT is backed by the US and is helping to train police and soldiers bring more security among local communities.
It is regarded as a key part of a new US push to stabilise southern Afghanistan, where remnants of the Taleban and al-Qaeda remain active more than two years after being driven from power by US-led forces.
The aid workers killed on Wednesday had been involved in government projects to rebuild the rural economy, correspondents say.
They belonged to the Serai Development Foundation, a group involved in rebuilding roads and providing clean water.
More than 550 people, including many rebels, have been killed since August.
A leading aid worker said the latest attacks showed the urgent need to boost provincial security, and that the policy of relying on PRTs for security instead of large bodies of peacekeepers was flawed.
"This is an extremely serious incident which is very, very shocking to the NGO community," said Afghan Relief spokeswoman Barbara Stapleton.
"We are extremely concerned about the security situation," she said.
"We do not see that the international community's response in terms of the PRTs as a being adequate for the highly complex security challenges we face in Afghanistan."