Thousands of people have died in the crackdown that began when Duterte took office in the middle of last year.
Thousands of people have died in the crackdown that began when Duterte took office in the middle of last year, with rights groups warning police are carrying out extrajudicial killings not just to fight crime but to aid their own corrupt activities.
Duterte won the presidential elections largely on a law-and-order platform headlined by a vow to eliminate the illegal drug trade in three to six months.
Once in office Duterte extended the timeframe until March of this year, but on Monday he said there would be no end while he was in power.
"I will extend it to the last day of my term," Duterte told reporters.
"March no longer applies."
In the Philippines, presidents are allowed to serve only a single term of six years.
Duterte has been unrepentant in the face of fierce criticism of the drug war from various Western governments, UN agencies and rights groups, saying he must take extreme measures to stop the Philippines from becoming a narco state.
However a series of scandals involving the police using the drug war as a cover for extortion, including the abduction and murder of a South Korean businessmen, have fuelled fears that rogue cops are on the rampage.
Police chiefs had repeatedly insisted in recent weeks that those crimes were isolated cases, and that they did not signal a larger problem.
However Duterte said on Monday he believed almost 40 percent of all police officers around the country were involved in graft.
"You policemen are the most corrupt. You are corrupt to the core. It's in your system," Duterte told reporters as he railed against the officers who allegedly masterminded the murder of the South Korean businessman.
He said he wanted to "cleanse" the police force by doing a review of all the police officers that had previously been involved in extortion.
However Duterte had previously insisted on many occasions he would not allow any police officer to go to jail for killing people in the name of his drug war.
He also said last year he would be "happy to slaughter" three million drug addicts as part of his crime war.
Police have reported killing more than 2,500 people they have accused of being drug suspects, while nearly 4,000 others have died in unexplained circumstances in the crackdown, according to official figures.