Washington ? Attorney General Eric Holder sought support Wednesday for erasing the gap in prison sentences for crack and powder cocaine crimes, a disparity that hits black defendants the hardest.

The effort to change federal sentencing laws for cocaine has broad support but may still unravel amid disagreements about how equal the sentences should be, and whether the whole sentencing system needs to be changed.

“One thing is very clear: We must review our federal cocaine sentencing policy,” Holder said at a legal discussion sponsored by the Congressional Black Caucus.

Under current law, it takes 100 times more powdered cocaine than crack cocaine to trigger the same harsh, mandatory minimum sentences.

“This administration firmly believes that the disparity in crack and powdered cocaine sentences is unwarranted,” Holder said. “It must be eliminated.”

The law was passed in the 1980s during the spread of crack in American cities, which officials blamed for a rise in violence. Yet in the years since, worries about crack have declined.