Pilot reported Auto Throttle problems on climb out. Excessive force was required to manually move the Left Throttle and Auto Throttle was unresponsive. The Flight Crew determined the best course of action was continue to destination airport; operating the Throttles manually.

Narrative

After departing Runway XXL; climbing through 1;500 feet; immediately after selection of VNAV; the LEFT Thrust Lever was unresponsive; remaining at T/O 1 Thrust and the RIGHT Thrust Lever began to Retard to reference climb thrust. The Left Thrust Lever was vibrating as if the Clutches were attempting to modulate it. After manually attempting to override the Auto throttles (A/T) is was determined that the Left Thrust would not move with a reasonable amount of force.The A/Ts were disconnected with disconnect switch as well as the A/T Arm Switch. Several attempts were made to move the Left Thrust Lever manually and only on the 3 attempt did it move with a force estimated at 10-15 pounds. It was determined that a physical stop existed in the LEFT Thrust Lever somewhere between T/O 1 thrust and adequate climb thrust. That region was available but would require the aforementioned force to modulate it within that range. With all things considered; the destination of ZZZ was considered the best option for landing. The area on the throttle quadrant of concern was never needed during the remainder of the flight which allowed for an uneventful decent approach and landing.