Some western countries and human rights groups have strongly criticized Duterte's anti-narcotics campaign that has killed more than 3,900 suspected drug users and peddlers, in what the police called self-defense after armed suspects resisted arrest.
He said at the time: "I was really looking for a confrontation so I could kill".
Trump is due to fly into Manila from Vietnam along with many other leaders on Sunday evening, ahead of two days of talks.
As US President Donald Trump prepares to meet leaders at the Association of Southeast Asian Nations (ASEAN) summit in the Philippines capital of Manila on 12 and 13 November 2017, Amnesty is calling on him to condemn President Duterte's murderous "war on drugs", and push him to investigate the unlawful killing of thousands of people around the country. "Stabbing. That was when I was 16 years old, just because we just looked at each other", he added, prompting laughter from the audience. I got information from Secretary Bong Go who is the Special Assistant of the President that although it was short, it was warm and cordial.
Hultgren, a Republican lawmaker from IL, and McGovern, a Democrat representative from MA, are co-chairmen of a US congressional panel on human rights.
Duterte went on to say that he "won't let you off the hook" if you mess with Filipinos, adding, "Never mind about the human rights advocates".
Philippines President Rodrigo Duterte has admitted stabbing someone to death when he was a teenager. So again, I thank you very much, the Russian people, and you, Mr. President.
Philippine President Rodrigo Duterte, who is facing global criticism for his bloody war on drugs, said his country was willing to host a "world summit" to tackle how nations can protect human rights.
Duterte boasts that as mayor of the southern city of Davao, he has killed suspects to serve as an example to his police officers. "Just to show the guys that, if I can do it, why can't you?"
Hultgren and McGovern highlighted the significant increase in the number of alleged extrajudicial killings in the Philippines, citing a 2016 human rights report by the US Department of State.
The Philippine leader praised the caliber of "high-precision" Russian weapons and their use in a new type of warfare involving snipers and fights that would take place "house-by-house" in Marawi City. Since then, Philippine police have reported killing almost 4,000 people.
A spokesman for Duterte said the remarks had been made "in jest".