White House aides are fretting over a proposal by Attorney General Janet Reno and drug czar Barry McCaffrey to relax federal sentences for selling small amounts of crack cocaine and increase them for selling powder cocaine. The plan endorses complaints that federal law treats crack, used chiefly by minorities, 100 times more harshly than powder - amounting to a “symbol of racial injustice.” Aides worry that Clinton will be called soft on drugs if he backs the plan.