A huge Congolese hydroelectric scheme has been dealt a blow by mining giant BHP Billiton's decision to abandon plans for an aluminium smelter.
The foundry would have been powered by the planned Inga Three hydro project, providing it with a major customer.
The firm said it decided to pull out after a review of construction costs.
The Democratic Republic of Congo's Inga Three would add to two existing dams on the Congo River, making it Africa's largest hydropower dam.
The project is seen as crucial to providing sufficient power by 2020 and spurring the country's economic growth.
DR Congo's multitude of rivers offer enormous hydropower potential, but a lack of infrastructure and difficult business climate have made it difficult to find investors - leaving the vast majority of the country in darkness.
"The company has chosen to not continue the [smelter] project, which was still at a very early stage, following a review of its economics," BHP Billiton spokesman Ruban Yogarajah told the Reuters news agency, adding that the firm would not have been the only customer of Inga Three.
Correspondents say the pullout of the Australian-based multinational is significant because the mining company would have been a major - and solvent customer.
The dam would also have provided electricity for the Congolese national grid.
The DR Congo government says it is confident of finding other backing for the scheme - which has been considered for many years, but never received sufficient backing.
"The problem is real but there are alternative solutions," Energy Minister Gilbert Tshiongo told Reuters.
Inga Three, near the estuary of the Congo River, is estimated to cost between $8bn and $10bn (£5-£6bn) and would produce 3,500 to 7,000 megawatts.
The plan has been stalled for several years with the African Development Bank warning over the costs - but last year it received a boost when DR Congo and South Africa signed an agreement to build Grand Inga, another much more ambitious hydropower scheme.
World Bank studies show that project would cost $50bn and could take decades to build, but would produce twice as much electricity as China's Three Gorges dam.
A mining boom in the mineral-rich southern province of Katanga has put additional strain on DR Congo's inadequate power resources.
The government last year said Inga Three was planned to come on line in 2018.