The sea phase of 26th edition of Singapore India Maritime Bilateral Exercise (SIMBEX)-19 commenced in the South China Sea from Sunday.
To contrast, the US Government promotes energy security for those Southeast Asian nations, he said in his address to one of the largest gathering of global energy leaders.
When asked if the US was concerned about China's actions, Pompeo replied "absolutely," adding that Washington has a national security strategy to address the problem.
Indian Ambassador Gautam Bambawale spoke candidly on a host of issues including unresolved India-China boundary question.
Trade tensions between the US and China over Beijing's technology policy and other market access issues have added to strains within the region, especially since Trump took office in early 2017.
Beijing's comments appeared to be the first clear timeframe for finishing the code of conduct.
The final sea phase would be held in the Bay of Bengal from 19 to 21 November.
Despite the frank airing of differences at the meeting in Washington of the two nations' top diplomats and military chiefs, both sides stressed the need to tamp down tensions
The United States rejects China's territorial claims and routinely says the military will "continue to fly, sail and operate wherever international law allows at times and places of our choosing."
Mattis's remarks came after Beijing voiced "strong dissatisfaction" on Sunday after two US warships sailed by an island in the disputed Paracel Island chain.
China has voiced "strong dissatisfaction" after two US warships sailed by an island claimed by Beijing in the disputed South China Sea, adding to simmering tensions in the strategic waterway.
China and members of the Association of Southeast Asian Nations have held their largest- ever joint maritime rescue exercise, signalling a lull in South China Sea tensions.
US President Trump decries threats to sovereignty in Ukraine, South China Sea at the UN General Assembly
US President Donald Trump on Tuesday decried threats to sovereignty in Ukraine and the South China Sea.
China today lodged a diplomatic protest with Japan over its defence white paper which criticised Beijing's aggressive policies in the South and East China seas.
Southeast Asian nations issued a diluted statement on the dispute and agreed to Beijing's terms on talks over the decades-long dispute at ASEAN today.