JOHANNESBURG A group of U.S. lawmakers is calling for a U.S.-Africa trade summit planned for later this year to be moved from South Africa in response to what they said was the country's "deepening military relationship" with Russia.

In a letter to U.S. Secretary of State Anthony Blinken and other senior officials, they also suggested South Africa is in danger of losing its benefits under the African Growth and Opportunity Act (AGOA) - Washington's flagship trade programme.

South Africa is due to host the AGOA Forum in Johannesburg, a meeting of African leaders and U.S. officials to discuss the future of the programme, which is slated to expire in 2025.

South Africa's exports to the U.S. under AGOA reached nearly $1 billion in the first three months of this year, making it the second biggest beneficiary of the programme after Nigeria.

African nations are seeking to extend AGOA, which grants qualifying countries' exports preferential access to the U.S.

"We are seriously concerned that hosting the 2023 AGOA 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.

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.

However, 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.

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.

(Reporting by Joe Bavier; Additional reporting by Carien du Plessis; Editing by William Maclean)