In a speech before the troops in Mactan in Cebu City in the central Philippines, Duterte said that he has accepted the offer of Moro National Liberation Front (MNLF) founding chairman Nur Misuari to integrate some 2,000 to 3,000 MNLF fighters into the Armed Force of the Philippines to help crush the Maute group.
The government security forces are now fighting close to 200 to 250 Maute militants holed up in the southern Philippine city of Marawi. The group has pledged loyalty to the ISIS.
Fighting between the government troops and the Maute militants broke out on May 23 when the militants tried to occupy Marawi in a bid to make it a caliphate for ISIS. The military said 120 militants, 30 civilians and 38 soldiers and policemen have been killed in the sporadic fighting.
"I am ready to integrate them (the 2,000 to 3,000 able-bodied MNLF fighters) into the AFP. I have no problem with that," Duterte said.
Duterte said Misuari made the offer during a "late talk" on Saturday night with him. "I accepted the offer," he said.
He added, "I am offering even to MILF (Moro Islamic Liberation Front). If you want to join us you are also invited including the regulars of the NPA (New People's Army)."
"To all the NPAs I can also take you in, just bring the guns, I will replace them with new ones, and you'll be enlisted in the armed forces," Duterte said.
Duterte did not give details on how these rebel forces will be integrated in the AFP.
Duterte declared martial law in Mindanao and nearby island provinces after the Maute group attacked Marawi on May 23.
Both MILF and the MNLF were initially founded with the aim to establish a caliphate and alleged the government of fostering the Christian faith and subversion against Muslims.
The Moros have accused the central government of long neglecting the Mindanao region economically, encouraging Christian settlement and supporting corrupt politicians to weaken Muslim influence.
The MILF is now the biggest Muslim rebel group in the Philippines. The MNLF forged peace with the government in 1996. However, the agreement failed to bring lasting peace in Mindanao.
The Duterte administration has canceled its scheduled peace talks with the communist rebels.