President Rodrigo Duterte said on Wednesday he confronted United States Ambassador to the Philippines Sung Kim on America 's inaction when China was aggressively building artificial islands in the disputed South China Sea .

In a speech in Socorro, Oriental Mindoro, Duterte recalled his conversation with Kim, who called on him last Monday in Davao City .

"I told him, you know, I'm surprised really Mr. Ambassador because had America really wanted to avoid trouble early on, when overflight was shown in the newspaper, there was something brewing, there was something as if a runway was being built, there were some concrete buildings on the coastal side, said Duterte.

Why did you not send the Armada of the 7th Fleet, which is stationed there at the Pacific to just make a U-turn and go there and tell them (China) right on their face, 'stop it'," Duterte said.

He noted "another set of law says you cannot make man-made structure in the high seas."

But Kim's answer was apparently evasive. Duterte said the US envoy told him that he was on another assignment, which was in North Korea .

China built structures in seven shoals and reefs in the South China Sea despite strong protests by other claimants, including the Philippines .

US think-tank Asia Maritime Transparency Initiative has reported China seems to have finished major construction of military infrastructure on artificial islands.

China has continued with its development in its occupied areas despite the July 2016 ruling of the United Nations Arbitral Tribunal favoring the Philippines and invalidating Beijing claim in almost the entire South China Sea .

Duterte said when he undertook a state visit to China in October last year, while he did not insist on the arbitral ruling, he made it a point to tell President Xi Jinping the Philippines has not abandoned its claim.

When he assumed office, Duterte declared a softer stance with China .

The president expressed belief he "made the correct decision" for taking a friendly stance with Beijing .

He noted the Philippines ' agricultural exports could easily enter China .

He even credited the "kindness" of Xi and the Chinese people and described them as "faithful friends." Celerina Monte/DMS