A memo from the Office of Management and Budget tells federal agencies to more closely enforce such laws, as part of Donald Trump's bid to put America first when it comes to trade.
Agencies are told to limit exemptions and to draft policies to maximize the procurement of U.S. products, especially steel, iron, aluminium and cement.
The 1933 Buy American Act requires the Pentagon to purchase domestically-produced products for purchases costing more than $3,500, while the 1941 Berry Amendment applies mainly to clothing and food products purchased by the military.
However, a number of free trade agreements grant American defense manufacturers exemptions when it comes to sourcing materials from outside the U.S.
The letter said that billions of dollars worth of goods were purchased every year under exemptions and called for the application of waivers to be carefully monitored.
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