Philippine President Rodrigo Duterte today warned US President Barack Obama and other foreign leaders not to question his deadly anti-drug campaign when they meet at an annual South-East Asian summit in Laos.

"You must be respectful," Duterte said before flying to Vientiane, where he makes his international debut at the Association of South-East Asian Nations (Asean) leaders' summit after becoming president on June 30.

"Son of a bitch, I will swear at you at that forum," he added, when asked how he would respond to questions about the spate of killings of suspected drug users and addicts under his administration.

According to police statistics, 1,011 suspected drug users and pushers have been killed in police operations from July 1 to Sept 4.

Police also recorded 1,391 deaths that are still being investigated during the same period.

Duterte was scheduled to hold a one-on-one meeting with Obama tomorrow after the start of the Asean leaders' summit.

He would also meet with his counterparts from Russia, Australia, Japan, India, New Zealand, Singapore, Laos and Vietnam.

Last week, White House press secretary Josh Earnest said Obama was "not going to pull any punches" on human rights when he meets with Duterte.

While Duterte stressed that he does not want to pick a fight with Obama, he added: "Nobody but nobody should interfere. This is an independent country. Nobody has the right to lecture on me... If you do that, we will end up insulting each other."

- dpa