Presidential spokesman Harry Roque on Friday said Duterte also approved during a meeting with Cabinet officials the extension of a lockdown in metropolitan Manila and several provinces and cities up to May 15.
A lockdown in the main northern Luzon region of more than 50 million people is set to expire on April 30.
"I'm warning everybody and putting the armed forces and the police on notice that I might declare martial law. There will be no turning back," Duterte said in a televised speech beamed nationwide.
"I have two more years. I will try to finish all of you, including you the legal (fronts), you should go and hide."
Duterte renewed his attacks on the New People's Army guerrillas, who he said has extorted large amounts of money from big companies and stole firearms of slain soldiers in an insurgency that has dragged on for more than a half century.
The rebels have denied his accusations and said they were helping villagers cope with the pandemic.
The Philippines has reported nearly 7,000 cases of COVID-19 disease, including 462 deaths.
It's among the highest in Southeast Asia but many believe the toll is higher given the limited coronavirus tests specially in provincial and rural regions. (AP) SCYSCY