Spanish to English Tech/Engineering Computers: Systems, Networks this involves a call-for-bids

This refers to a call-for-bids to supply radio communications equipment. The full sentence reads:
"Estos archivos deberán contener la totalidad de antecedentes exigidos por el Mandante para cada una de las presentaciones."
My question is this: What would we call the "Mandante" in English? This is the party to whom the bids will be submitted -- i.e., the contracting party. In another context, we might use the word "Principal" (as in a power-of-attorney), but I don't think that fits here.

THANK YOU!