Concerns over the plans to build 12 dams on the Mekong River - dams would impact the environment and food security in the region

As the United States is a donor to the mekong River Commission (MRC), the committee was urged to do everything in its capacity to ensure that mainstream dams would not proceed until the findings of the MRC-commissioned Strategic Environmental Assessment were considered and adopted by regional governments.

Cambodia, Laos, Thailand and Vietnam are members of the MRC, which is a regulatory body to oversee the lower mekong basin.

The United States has paid more attention to the mekong River since Washington formed closer links with the four countries in the basin under the framework of Mekong-Mississippi Rivers cooperation last year.

The hearing took place a day after the MRC said it had received official notification from Laos that the country would proceed with the Xayaburi project, as the first dam in the mekong mainstream, according to conservationist International Rivers.

Aviva Imhof, campaigns director for International Rivers, testified before the committee.

Imhof relayed to the committee the Strategic Environmental Assessment's findings and its recommendation that any decision on mainstream dams be deferred for at least 10 years.

"To allow the Xayaburi consultation process to go forward without considering the findings would be like getting a diagnosis of cancer and then ignoring it," she said in a statement.

Webb said the mekong fisheries were important for food security in the region, and expressed concern about the dramatic impact that could occur to livelihoods and the river ecosystem if the dams were built. The dam plans were "profoundly disturbing" on the political, economic and social levels, he said.

The Xayaburi Dam would be the first to be built on the lower Mekong. It would displace thousands of people in Laos, disrupt an important fish migration route and cause the extinction of the critically endangered mekong giant catfish by destroying one of its last natural spawning habitats.

The dam is being proposed by Thai company Ch Karnchang and more than 95 per cent of the power generated would be sold to Thailand.

This month, Thai community groups representing about 24,000 people in five provinces along the mekong River submitted an appeal to Prime Minister Abhisit Vejjajiva asking him to cancel the plan to buy electricity from the Xayaburi Dam.