A drive system includes an output shaft of an engine connected to a sun gear of a planetary gear assembly. An electric motor is connected, via gears, to a carrier rotatably supporting a planetary pinion gear that rotates around the outer circumference of the sun gear while rotating on its axis in engagement with the sun gear. An input shaft of a STEPTRONIC.TM. transmission is connected to a ring gear that rotates in engagement with the planetary pinion gear. The drive system further includes an engine clutch directly coupling the output shaft of the engine to the ring gear, a ring gear brake that regulates the rotation of the ring gear, and a torque converter clutch and a torque converter for transmitting the driving force of the electric motor to an output shaft of the STEPTRONIC.TM. transmission.