Brake Problem

I have a 1991 Jeep Cherokee, in line 6 cyl. When I first start the car and engage the auto transmission. the break waring light comes on as well as the anti-lock brake lite comes on. I don’t seem to have power breaks and the car is hard to stop. I can barley get the car to stop when I press the brake peddle to the floor. After I have driven about a mile, the lights go off and I have normal breaking. The car stops fine. ???????????? Help!