The negotiators were trying to square the circle by satisfying both parties completely.
Переговорщики пытались достичь невозможного, полностью удовлетворив обе стороны.
Definitions
To attempt to do something that is impossible or extremely difficult; originally refers to the mathematical problem of constructing a square with the same area as a given circle using only a finite number of steps with compass and straightedge, which has been proven impossible.