MD80 flight crew reports runway excursion while attempting to expedite takeoff at towers request with icy runway conditions.

Narrative

The aircraft weight was 113;000 LBS and the STAB trim setting was 3.7. 54 passengers were on board. Only 2 were in First Class. There were several inches of snow on the ground as well as snow and ice on the ramp; taxiways; and the runways. While taxiing to Runway XXL; the Tower cleared us for an 'expedite' takeoff due to traffic on final for Runway XY. As we entered the runway; the Captain pushed the throttles forward. I noticed that the right engine accelerated rapidly to approximately 1.4 EPR while the left engine remained at idle power. As the aircraft approached the centerline of the runway; I noticed that the aircraft was not turning to align with the runway heading. I alerted the Captain to the situation and looked over to see if he was OK. He retarded the throttles to idle; turned the nosewheel steering further to right and began to apply the brakes. The aircraft slid off the left side of the runway at a low speed. The aircraft stopped the runway edge and the distance remaining markers. I believe the incident was caused by ice on the runway. The low weight on the nosewheel and asymmetric thrust due to slow acceleration of the left engine were contributing factors. I recommend loading the aircraft with a greater forward center of gravity when snow or ice exist on the airport. I also recommend that the ground and tower controllers be prohibited from issuing 'expedite' clearances when ice and snow are on the airport.