U.S. National Security Advisor Robert C. O’Brien attends 7th ASEAN-United States Summit in Bangkok, Thailand, November 4, 2019. REUTERS/Soe Zeya Tun

BANGKOK (Reuters) - A U.S. envoy to a leaders’ summit in Southeast Asia criticized China’s actions in the disputed South China Sea as akin to “conquest”.

White House National Security Adviser Robert O’Brien said the disputes over territorial waters claimed by China and several Southeast Asian countries should be handled peacefully.

“We don’t think they should be handled by intimidation or through maritime militias or by random ships or by surrounding islands,” O’Brien said. “That’s just not how things should be done in the 21st century. That’s conquest.”

Nevertheless, O’Brien said Washington sought a “great relationship” with China, saying the two sides were close to a “phase one” agreement to begin to roll back a 16-month trade war between the world’s two largest economies.