The US Commerce Department has launched a probe into alleged dumping by several foreign steel producers accused of undercutting America's domestic industry.
Japanese producers were selling hot-rolled steel flat products into the United States at 16 percent under the market prices while producers from Turkey discounted their steel by one-third.
South Korea is the largest supplier of cold-rolled flat steel to the United States, exporting $678.8 million worth last year.
The probe was brought on behalf of major US steel producers who have been hit with competition from cheaper imports as the global steel industry endures a supply glut, mainly due to China's downturn.
The Commerce Department said it would reach a preliminary determination on the probe by September 25, and could set anti-dumping and anti-subsidy duties beginning as early as November.