U.S. Secretary of Commerce Wilbur Ross shakes hands with China's Premier Li Keqiang, as U.S. National Security advisor Robert O…
U.S. Secretary of Commerce Wilbur Ross shakes hands with China's Premier Li Keqiang, as U.S. National Security advisor Robert O'Brien watches, as they attend a bilateral meeting on the sidelines of the 35th ASEAN Summit in Bangkok, Nov. 4, 2019.

BANGKOK - U.S. national security adviser Robert O'Brien denounced China's ongoing military buildup in the South China Sea at a meeting of Southeast Asian leaders in Thailand Monday.

"Beijing has used intimidation to try to stop ASEAN nations from exploiting their off-shore resources, blocking access to 2.5 trillion dollars of oil and gas reserves alone. These tactics go against the rules of respect, fairness, and international law. The region has no interest in new imperial era where a big country can rule others on a theory that might make it right," he said.

In comments apparently aimed at Washington, China's Vice Foreign Minister Le Yucheng criticised what he called "meddling" by powers outside the region in negotiations to resolve the territorial dispute

"Regrettably, as the saying goes, while the tree desires tranquility the wind keeps blowing. Some non-regional countries cannot live with calm waters in the South China Sea and have come all the way to this part of world to make waves and create tensions," he said.

Despite the heated rhetoric between Washington and Beijing, O' Brien and Premier Li Keqiang held bilateral talks on the sidelines of the summit.

O'Brien also read a message from President Donald Trump during his speech inviting the ASEAN leaders to join him in the U.S. for a special summit" in the first quarter of 2020.  

China has made sweeping maritime claims in the resource-rich waters of the South China Sea, and angered neighbours by sending ships into the busy waterway, where several members of the Association of Southeast Asian Nations, also known as ASEAN, also have claims.