US Defence Secretary Donald Rumsfeld has said major combat operations in Afghanistan are at an end.
Rumsfeld has called for more support for President Karzai
He said the country had moved into a period of stabilisation and reconstruction.
Mr Rumsfeld was speaking in Kabul after talks with President Hamid Karzai.
A BBC correspondent in the Afghan capital says there is growing frustration there at the slow pace of change, and continuing concerns about security.
"We are at a point where we clearly have moved from major
combat activity to a period of stability and stabilisation and
reconstruction activities," Mr Rumsfeld told reporters at the end of his brief visit.
But he stressed: "There are still dangers, still pockets of resistance, in parts of the country."
President Karzai said Afghanistan had made great progress since the country's former Taleban rulers were overthrown 18 months ago.
But he said much more needed to be done, and that his administration lacked resources.
The US still has some 10,000 troops stationed in Afghanistan following the overthrow of the Taleban.
A dead US soldier is flown home
The troops have been involved in frequent encounters with suspected remnants of the Taleban and the al-Qaeda network, with four US troops killed since March.
The US has said it expects its troops to remain in Afghanistan for years. Security is a constant problem for Mr Karzai's government.
A number of his ministers have been killed and the president himself survived an assassination attempt in the southern city of Kandahar last September.
In addition, there have been signs recently that the Taleban has been regrouping in the south-east of the country.
Both the US and the Afghan Government are concerned by the ability of enemy fighters to move across the border from Pakistan.
Last year Mr Rumsfeld urged the international community to do more to support Mr Karzai, although he insisted that the overall security situation in Afghanistan was better than it had been for 25 years.