US Secretary of State Mike Pompeo on Thursday criticised China's dam-building on the Mekong River, saying its construction had left the crucial waterway at its lowest level in a decade in Southeast Asian countries downstream.
Mr Pompeo spoke in Bangkok, where he met ministers of the Lower Mekong Initiative countries, who complain of drought caused in part by upstream dams on the river.
"The river is at its lowest levels in a decade, a problem linked to China's decision to shut off water upstream," Mr Pompeo said.
Drought in Thailand, which is hosting this week's meeting of foreign ministers from the Association of Southeast Asian Nations (Asean) and others, including China and the United States, has severely affected farmers and the government has asked them to delay planting rice crops.
The US secretary of state also told his Southeast Asian counterparts on Thursday that the United States had never asked Indo-Pacific nations to take sides.
Regional rivalry between the United States and an increasingly powerful China hangs over this week's security meetings.
"Look, we don't ever ask any Indo-Pacific nations to choose between countries," Pompeo said at the start of the meeting.
"For decades, American diplomacy with Asean has been consistently guided by our desire for partnership, our respect for the sovereignty of each of our nations and our shared commitment to the fundamental rules of laws, human rights, and sustainable economic growth," he said in brief remarks.