A drive-steering control system suitable for off-road land and amphibious vehicles. The system includes first and second steering input levers, each operable to rotate in forward and rearward pivotal directions. A coupling mechanism converts and transmits rotation of the first steering input lever in the forward pivotal direction into rotation of the second steering input lever in the rearward pivotal direction, and vice-versa. A reducing mechanism operates to selectively reduce the propulsion outputs of first and second propulsion devices, and a converting mechanism operates to convert the rotations of the steering input levers into inputs to the reducing mechanism. Depending on the directions the steering input levers are rotated, the reducing mechanism reduces the propulsion output of either the first or second propulsion device, which causes either the lefthand or righthand side of the vehicle to travel at a lower speed and thereby turn the vehicle either left or right.