U.S. Secretary of State Hillary Rodham Clinton praised Laos as taking a "forward-leaning position" after the tiny, land-locked nation said it had no immediate plans to resume work on a dam across the Mekong River.
The project Laos was considering would be the first dam across the river as it meanders through Myanmar, Laos, Thailand, Cambodia and Vietnam. China has dammed its upper reaches, but the 3,000-mile (4,900-kilometer) river otherwise runs free.
Opponents say construction in Laos could open the way for 10 more dams downstream. That would affect the lives of hundreds of millions of people.
"This is a serious issue for all the countries that share the Mekong River," Clinton said at a meeting of ministers from affected nations Friday.
"Because if any of you build a dam, all of you will feel the consequences in environmental degradation, challenges to food security, and impacts on communities."
Laos announced in May that it would defer building the $3.5 billion Xayaburi dam until an expert review was done. Hydropower is one of Laos' few major resources, and the country had hoped revenue from the dam would spur economic and social development.
It said Friday the suspension would continue, said Kurt Campbell, the top U.S. diplomat for Asia, though he provided no details.
Laos has said the dam would not significantly impact the Mekong mainstream, but activists, scientists and officials in other countries say it would cause irreversible damage.
"I want to urge all parties to pause on any considerations to build new dams until we are able to do a better assessment of the likely consequences," Clinton said.