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 conflict.
The lawmakers also appeared to back up an accusation by the U.S. ambassador to South Africa that a sanctioned Russian vessel collected weapons at a South African naval base last year.
South African officials say they are not aware of such an arms transfer and have launched an independent inquiry into the incident.
Persons:
Russia S.Africa, Antony Blinken, AGOA, Clayson Monyela, Cyril Ramaphosa, Vladimir Putin, Antony Blinken's, Joe Bavier, Carien du, William Maclean
Organizations:
AGOA, Twitter, State Department, White, SA, Africa's Department of Trade and Industry, South, International Criminal, U.S, Thomson
Locations:
Johannesburg, U.S, Africa, Washington, Russia, JOHANNESBURG, South Africa, South, Nigeria, Ukraine, United States, China, Russian