China rebuts the U.S. criticism on Beijing's dam-building affecting the water level in Southeast Asian countries downstream as "irresponsible" and "groundless" on Friday.

Chinese State Councilor and Foreign Minister Wang Yi made the remarks on the sidelines of the ASEAN Foreign Ministers' Meeting in Bangkok.

U.S. Secretary of State Mike Pompeo complained on Thursday that China's dam-building on the upstream of Mekong River had left the crucial waterway at its lowest level in a decade in downstream areas.

In response, Wang said China noted there's drought on the downstream of Mekong River and has actively increased water discharge to it to help cope with the situation.

Lancang River, which runs through three provincial-level regions in China as part of the upstream of Mekong River, only accounts for 13.5 percent of the river's total runoff volume, Wang said.

"And the water volume in the Mekong River is mainly affected by downstream retention and rainfall," Wang added. "Lancang-Mekong River is crucial for both China and ASEAN countries and countries along both the downstream and upstream have maintained close cooperation."

The Lancang River originates in northwest China's Qinghai Province, continues to flow through Tibet Autonomous Region and Yunnan Porvince, both in southwest China, and, once out of the Chinese border, flows through the heart of Southeast Asia. Once it streams through Myanmar, Laos, Thailand, Cambodia and Vietnam, it is called the Mekong.