"We are seriously concerned that hosting the 2023 African Growth and Opportunity Act Forum in South Africa would serve as an implicit endorsement of South Africa's damaging support for Russia's invasion of Ukraine," the letter, dated June 9, stated.
In a letter to U.S. Secretary of State Anthony Blinken and other senior officials, the Members of Congress also suggested South Africa is in danger of losing its benefits under the AGOA - Washington's flagship trade program.
The lawmakers voiced frustration with South Africa's hosting of joint naval operations with China and Russia in February, and plans to hold a summit of BRICS leaders - where Russian President Vladimir Putin is invited despite being charged with war crimes by the International Criminal Court.
Referring to the letter, South African foreign ministry spokesman Clayson Monyela said on Twitter: "There is no decision by the State Department/White House to move the AGOA Forum from SA."
South Africa's Department of Trade and Industry, which manages the country's trade relations with the United States, said it was not planning to respond publicly to the letter.
South Africa's government has declared its neutrality in the war in Ukraine, and President Cyril Ramaphosa is participating in an effort by African leaders to mediate in the Russia-instigated conflict.
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