By Ian MacWilliam
BBC correspondent in Kabul
The American company building one of Afghanistan's most important roads says that security concerns about the project have now been largely overcome.
Paving work is to begin shortly on the highway from the capital Kabul to the southern city of Kandahar.
The road is one of the key reconstruction projects necessary to improve Afghanistan's economic and political stability.
For years, Afghanistan's most important highway, linking the capital with Kandahar, has been a pitted strip of potholes and shell holes.
Vehicles have taken two days to crawl the 500 km between Afghanistan's two most important cities.
President George Bush, however, promised the Afghan president, Hamid Karzai, that America would build a black-top road to link the cities by the end of this year.
Potholed and shell-damaged roads are often a traffic hazard
Earlier, work was held up for six weeks after a number of Afghans clearing mines from the road were killed by presumed Taleban or al-Qaeda supporters.
The American company in charge of the $200m project, the Louis Berger group, says some 800 Afghan policemen are now patrolling the highway to ensure security, and work is going ahead seven days a week.
The entire road length has been graded, already reducing the journey time to around 10 hours.
The company expects to begin paving the road with asphalt in a few days' time.
Afghanistan has almost no good hard-top roads after years of war and neglect, so road-building is central to restoring the economy and extending Kabul's influence in the provinces.
The Kandahar road is to become Washington's showpiece project, demonstrating its continuing commitment to Afghan reconstruction.
President Bush is kept informed of its progress and there is considerable pressure to finish the promised road on time.
The next big road project will be the highway from Kandahar to Herat.
The Louis Berger group is already beginning to design that road, which would complete a road link between three of Afghanistan's four main cities.