The British Army's transport of the turbine to Kajaki was hailed as a big success
The US foreign aid agency USAid has indefinitely postponed the Kajaki hydroelectric power project in southern Afghanistan amid a lack of security.
Some 5,000 mainly British soldiers took five days last year to transport a huge turbine through Taliban-held territory to the dam in Helmand province.
USAid said the road was not secure enough for delivering cement needed to install it at the site.
A Chinese firm contracted for the purpose had pulled out, it added.
A convoy of 100 vehicles moved the massive sections of the turbine 180km (112 miles) in August and September last year.
It would have been the third turbine at the dam, which was originally built by USAid and supplies power to Helmand's provincial capital, Lashkar Gah.
UK Prime Minister Gordon Brown described the operation at the time as a reminder of Nato's "fundamental purpose" in Afghanistan.
British government departments contacted by the BBC on Monday would not comment on news the project had been postponed indefinitely.
'No secure road'
Interviewed earlier by the UK's Guardian newspaper, USAid's head of energy and water projects, John Smith-Screen, said the turbine parts were being packed away and the agency was looking for other Afghan energy projects to invest in.
"Our message is that until we have a secure road we cannot continue with the installation of turbine two," he said.
"When the turbine was moved in by British and American forces it was a huge effort and it was done in a point of time.
"But we can't move in the large quantity of cement and aggregate that we need in a point of time; we need a sustained effort."
The Chinese company contracted to install the turbine had left overnight for security reasons and the agency had not been able to find another sub-contractor to do the work, Mr Smith-Screen said.
Last year's convoy had travelled the length of the Helmand river valley through insurgent-controlled areas, carrying seven 20-30-tonne sections.
It was described as the largest route-clearance operation the British military had undertaken since World War II.
Around 1,000 other Nato troops from the US, Australia, Denmark and Canada were involved and 1,000 Afghan soldiers protected the turbine through one of the most dangerous legs of the journey.