The South African rand took a knock against a firmer dollar in early trade on Friday, as global markets remained on edge over U.S. President Donald Trump's tariff threats.

The United States has imposed a 30 percent tariff on all South African exports to establish what it called a ‘’more balanced and fair trade’’ and threatened more tariffs if Africa’s biggest economy retaliates.

Citing false claims that white South Africans are being persecuted, Trump has cut aid to the country, publicly berated its president in the Oval Office and invited Afrikaners - descendants of early European settlers - to come to the United States as refugees.