South Africa is mounting a formal challenge to a new U.S. tariff proposal that could further strain trade ties between Africa's most industrialized economy and one of its most important export markets.

The move comes months after President Donald Trump's administration imposed a 30% tariff on South African imports, a measure Pretoria warned would hurt key export industries including automobiles, agriculture, steel and manufacturing.

Now, South Africa faces another potential trade setback after the United States proposed a 12.5% tariff on imports from several countries, including South Africa, over concerns linked to forced labour in global supply chains.

In a detailed submission to U.S. authorities, South Africa rejected the basis for the proposed measure, arguing that the country already has robust laws and institutions to combat forced labour, human trafficking and unfair labour practices.

Trade, Industry and Competition Minister Parks Tau said South Africa had requested evidence from Washington to support allegations that goods produced through forced labour were entering the country or being re-exported to the United States.