But the project comes shrouded in uncertainty, including its main purpose—whether for shipping or irrigation—who will fund it, and how it will affect the flow of the Mekong—one of the world’s longest rivers.

Conservationists have long warned that the river, which supports up to a quarter of the world’s freshwater fish catch and half of Vietnam’s rice production, is at risk from infrastructure projects, pollution, sand mining, and climate change.

Cambodia, Laos, Vietnam, and Thailand are signatories to the 1995 Mekong River Agreement, which governs the distribution of the river’s resources.

While Cambodia is a close ally of Beijing, Hun Sen has denied the canal will be part of China’s Belt and Road infrastructure plan.