On Thursday, he met Cambodian strongman Hun Sen, a Beijing ally, and -- among a welter of projects for the poor Southeast Asian country -- offered to fund a new airport in Phnom Penh, a highway from the capital to the coastal city of Sihanoukville, and a hospital.

A joint statement after the state trip lauded the “important and fruitful outcomes of the visit”, which includes continued medical checkups in China for Cambodia‘s king and queen mother.

Observers say China often uses cash and soft loans for high-profile infrastructure projects to butter up its poorer neighbours.

The expressway alone would cost $2 billion, Cambodia’s transport minister Sun Chanthol told reporters later, without clarifying if it was newly-promised money.

The future of the Mekong river is a key strategic issue between the neighbours.

With control over the headwaters of the river -- known in China as the Lancang -- Beijing can dam its section while the impacts are felt downstream.

Communities in the lower Mekong countries have reported depleted fish stocks in recent years and are blaming the dams.

Environmental groups warn the blockages pose a grave threat to fish habitats by disrupting migrations and the flow of key nutrients and sediment -- not to mention displacing tens of thousands of people with flooding.

Experts say it is too early to draw full conclusions about the impact given a lack of baseline data and the complex nature of the river‘s ecosystem.

Li sent a far more reassuring message to forum participants in his remarks on Wednesday.

“We want to properly address the relationship between up- and downstream countries and accommodate the interests of all countries along the river,” he said. (AFP)