China plans to boost ties with Thailand, Vietnam, Cambodia, Laos and Myanmar through a series of infrastructure projects.
Foreign Minister Wang Yi met delegates from the five Mekong region nations on Friday in Chiang Mai, northern Thailand.
The attendees say they plan to improve the Mekong River's resistance to droughts and flooding.
And they say measures will be taken to prevent airborne pollutants known as PM 2.5 from crossing borders.
Wang told reporters that China will promote sustainable development in the region.
He also stressed Beijing's willingness to step up cooperation through rail, port and other projects.
Japan and the United States provide similar support to Mekong nations. Observers say China is attempting to expand its influence in the region.