Earlier in the day, a major Korean business lobby, Federation of Korean Industries, said it has asked 565 US lawmakers, officials and opinion leaders to press the Trump administration to reconsider the action.

"We understand the Trump administration's efforts to reduce the US trade deficits, but it has to reconsider the intensifying import restrictions on South Korean steel products," GS Group Chairman Huh Chang-soo, who heads the FKI, said in the letter.

The proposed steel duty is the latest in a series of US trade remedies, including safeguard duties imposed on Korean washers and solar panels earlier this year.

South Korea shipped 3.6 million tons of steel products to the US last year, becoming the No. 3 steel exporter after Canada and Brazil, according to the US Department of Commerce.

The new duties, in addition to the incumbent heavy tariffs, would sharply raise prices of South Korean exports, hurting their price competitiveness against American manufacturers, according to South Korean industry officials. (Yonhap)