He said he made the promise during a meeting on Monday night with the families of those killed in a shopping mall fire in the southern city of Davao.
Paolo Duterte tenders resignation amid drug smuggling allegations, squabble with daughter
Duterte's request, which is expected to be approved this week, added to critics' fears that the 72-year-old leader is seeking to steer the Philippines back into dictatorship.
Trump is due to land in the Philippine capital on Sunday evening ahead of two days of summits, and rights groups have urged him to pressure Duterte over the thousands of lives lost in the controversial anti-drugs crackdown.
Duterte goes into the event appearing confident that even his most outrageous remarks and actions will be ignored, having boasted in the lead-up he once stabbed someone to death, while at the same time proposing to host a global human rights summit.
Philippines' Duterte tells preschoolers: "I want world to be only for those who are good"
Philippines told the EU that it will no longer accept development aid from the foreign body.
China and Russia donated firearms while U.S. and Australia assisted with intelligence and military expertise
US Special Forces will stay in Mindanao as they are needed to provide capabilities that local military forces do not have
Second half of 2016 marked by ‘serious deterioration in respect for right to life, due process and rule of law’, report says
Vows to enforce the law equally to protect people and the republic
The EU can lead the drug war if they think they can solve the country’s drug problem
Jeepney operators and drivers held nationwide strike Monday and Tuesday
Duterte signalled in a fiery speech he would not tolerate European criticism of his drug war, which has seen police kill at least 3,850 people since he took office 15 months ago and led rights groups to warn of a potential crime against humanity.
President Rodrigo Duterte withdraws earlier order, gives military the option to end the battle in Marawi
Each of the dead men has a number in Roman numerals drawn in black pen above their bare feet to help the morticians keep track of the bodies that churn through each night. One of them is marked VI.
Moro Islamic Liberation Front to help intensify President Duterte’s war on drugs in areas under insurgents’ influence
Former Justice Secretary and current Senator Leila De Lima denies charges, calls herself victim of political persecution
The Philippines' longtime ally, the United States, has led international criticism of the killings, with outgoing President Barack Obama urging Duterte to prosecute his war "the right way".
President agreed last year to let both neighbors' navies enter Philippine waters to nab pirates kidnapping ships, tourists
Says authorities found link between drugs, terrorism and ongoing threat 'being fed with drugs'