President Rodrigo Duterte said on Friday that he would not fail in his war against illegal drugs because he is not stupid.

Duterte made the statement as he again hit former Columbian President Cesar Gaviria, whom he called as "insane." He previously called Gaviria as an "idiot."

"This former president was bragging that I am committing the same mistake. It's only possible Mr. ex-president if I'm stupid as you. But unfortunately, I am not," he said.

He said Columbia failed in its campaign against illegal drugs because the United States helped the Latin American country by spending billion dollars of funds.

Gaviria in his article in the New York Times said war on drugs could not be won through violence, citing Columbian experience wherein it became bloody and yet they did not succeed.

Since Duterte assumed office seven months ago, over 7,000 drug suspects have been killed. Of those who died, about 2,500 were during the police operations. Celerina Monte/DMS