Duterte won the presidency by a wide margin in 2016 on promises of eradicating drugs and crime, and recent opinion polls indicate broad support for him and for the crackdown, despite widespread allegations of police cover-ups and summary killings resulting from weak intelligence.
Duterte said the drugs problem was a national security issue, Presstv reported.
"I will not allow my country to end up a failed state because of drugs," he said in a speech.
He did not elaborate on how he would intensify a campaign that had already seen more than 5,000 people killed by police since he took office.
Human rights groups say many of those deaths were executions of people suspected of selling or using drugs, which police deny, insisting the killings were in self-defense.
Critics, including the Catholic Church, say the campaign has overwhelmingly targeted the urban poor and left drug kingpins largely untouched.
Asked by reporters later if the crackdown would be bloodier, Duterte said: "I think so."
A poll last week showed that about two thirds of Filipinos believed there were fewer drug users in their community now than last year. Most respondents said it was vital for police to arrest suspects alive and believed police agreed.