Saskatchewan Premier Brad Wall is wading back into the debate over proposed Buy American measures, which he views as harmful protectionism.

"Potential Buy American provisions ... [are] a potential threat to jobs and economic development on either side of the border," Wall said in a letter dated Oct. 3 to U.S. Senator Joe Lieberman, a leading Democrat.

The provisions are contained in a new job-creation bill.

The legislation would require public infrastructure work be done with U.S. made materials.

Wall says protectionist measures caused more harm than good during the Depression and the hurt now would be more severe because the economies are highly integrated.

"Lessons of history are only lessons if they are learned," Wall wrote. 

Wall was hoping leading American law makers would defeat the bill before Congress.

The premier, who is on the verge of calling a provincial election, spoke out against similar Buy American provisions in 2009.

Ottawa fought for more than a year to secure a Canada exemption,but that deal doesn't apply to the second round of stimulus being proposed by the Obama administration.