Prime interest rate slips back up to 20%

Citibank and Chemical Bank raised their prime rates to 20 percent from 19 1/2 percent, making that the prevailing rate among the nation's largest banks despite an easing in the money supply. Bankers Trust and Marine Midland Bank, which with Citibank had lowered the prime to 19 1/2 percent last week, went to the higher rate Friday.

The Federal Reserve reported a modest increase in the money supply Friday after three weeks of decline, which historically would signal lower interest rates. But the federal funds rate, which banks charge one another for loans -- a main source of funds -- has remained high, and analysts say interest rates won't come dow n until it eases substantially.