Laos's largest infrastructure project, the Nam Theun 2 hydropower development, is behind schedule but the power company said Monday it remains hopeful that the lost time can be made up.

Logistical problems in a heavy wet season caused "significant delays" late last year to completion of electro-mechanical works inside the power station, said Aiden Glendinning, spokesman for the Nam Theun 2 Power Company.

Heavy rains delayed the movement of equipment to the site in central Laos on the Nakai plateau, where it is being built on the Nam Theun river, a tributary of the Mekong.

"We've constructed lots of roads but it still can be tricky in the wet season," he said from Laos.

Efforts were made this year to recover the time lost but "while some ground has been regained, there are still delays in the schedule," Glendinning said, adding the contractors remain committed to meeting the December 15 deadline.

No official statement on the estimated completion date will be made before a board meeting early next month, he said.

The World Bank-backed development required about 8,000 workers operating on 14 separate construction sites spread over 200 kilometres (124 miles). Slight delays on a project of such a size and complexity "would not be unusual," the spokesman said.

Relocation of 6,301 villagers to make way for the project's reservoir was finished last June, he said, and the 450-square kilometer reservoir is now at about 90 percent of capacity.

After years of opposition from environmentalists, work on the 1.45-billion-dollar Lao-French-Thai project began in November 2005. It will have a generating capacity of 1,070 megawatts.

About 95 percent of production will be sold to Thailand, earning Laos revenues estimated at almost two billion dollars over 25 years, which the communist country pledged to spend on poverty reduction.

Critics said villagers were resettled to less fertile areas and expressed concern for the impact turbid river waters and erosion will have on fisheries and communities living downstream from the country's largest dam.