In a wide-ranging interview with Billboard magazine, the musician was asked about the disproportionate number of non-white people targeted by US drug enforcement policies.
"What it has become is not a war on drugs. It has become slavery. Or something crazier," Minaj said.
"When I see how many people are in jail, I feel like, 'Wait a minute. Our government is aware of these statistics and thinks it's OK?'. The sentences are inhumane.
"I love the president for trying to be a voice for people who no other person has ever tried to be a voice for."