Nations could soon be engaged in conflicts over access to water, Vietnam's president warned Friday, as he called for sustainable exploitation of Southeast Asia's Mekong River.

Speaking at a business forum in Russia, Vietnamese President Truong Tan Sang said water was likely to become a geopolitical flashpoint commodity like oil.

"It would not be over-exaggerating ... to view the water resources of the 21st century as the oil of the 19th and 20th centuries," Sang said during a seminar on water at the Asia Pacific Economic Cooperation event.

"Tensions over water resources are threatening economic growth in many countries and presenting a source of conflict especially given the efforts of all countries to step up economic development.

"Dam construction and stream adjustment by some countries in upstream rivers represents a concern for many countries and an implicit factor affecting relations between relevant countries."

The exploitation of the Mekong River -- the world's 12th longest river, has loomed as an increasingly divisive issue among nations through which it flows -- Myanmar, Laos, Thailand, Cambodia, Vietnam, and its source country China.

More than 60 million people rely in some way on the river, a vital transport waterway and the world's largest inland fishery with an annual estimated catch of 3.9 million tonnes, according to the Mekong River Commission.

But environmental groups warn the Mekong is threatened by over-damming for hydropower purposes.

Energy-hungry China has several planned or existing dams on the river but has rejected accusations they contributed to lower water-levels downstream.

Communist Laos, one of the world's most under-developed nations, promised in July to postpone building its Xayaburi dam after downstream Cambodia and Vietnam expressed concerns it could harm fisheries and threaten irrigation supplies.

Laos has said it would seek to address such concerns, but not cancel the $3.8-billion project.

"The management and efficient utilisation of water resources in the Mekong River represents a pressing issue with direct impact on (Vietnamese rice production)," Sang said.

Sang called for greater international cooperation to ensure the "sustainable exploitation and utilisation of water resources, particularly those running through different territories".