In a hastily-called news conference at the presidential palace, Duterte said he would not condone abuses and the police officers would have to face the consequences of their actions if that is the recommendation of a formal investigation.
"There is a possibility that in some of police incidents there could be abuses. I admit that," Duterte said.
Duterte unleashed a crackdown the day he took office on June 30 last year after a convincing win in an election in which he campaigned heavily on a promise to use deadly force to wipe out crime and drugs.
The firebrand leader, however, stepped back from defending the police as public anger mounts over the killing of Kian Loyd Delos Santos.
Civil society groups and left-wing activists marched in the streets to protest the killing.
There was also condemnation from Catholic bishops, senators and allies from education and other sectors. The police defended their actions, saying the boy was a drug courier.
Duterte said he called up the national police chief after seeing footage from a CCTV camera showing plain clothes police dragging the boy, who was later found dead after what official reports described as gunfight in a sting operation.
He said he would abide by the results of an investigation by the National Bureau of Investigation (NBI).
"If the NBI says we file charges of murder, sorry to the policemen concerned," he said.
"You have to face the justice system. They have to go to jail if convicted," he said.
He said there are some rogue elements in the police that were destroying the image of the government.
"These abusive police officers are destroying the credibility of the government," he added. "Who will follow the government if the credibility is destroyed?"
