The South Africa Democratic Alliance (DA) party leader John Steenhuisen told media his party had written to the FBI Pretoria Field Office "to request that they investigate allegations of possible money laundering by the president."
Cyril Ramaphosa is accused of hiding from police and tax authorities a 2020 break-in and cash heist from his luxury farmhouse in the northern Limpopo province.
Early this month, South Africa's ex-spy boss Arthur Fraser filed a police complaint alleging that thieves stole $4 million in cash from Ramaphosa's farmhouse, where the greenbacks had been stashed inside furniture.
The cash was said to be proceeds from the sale of animals at Ramaphosa's Phala Phala cattle and game breeding farm in Bela Bela.
Fraser accused the president of organizing the kidnapping and questioning of the robbers, and then bribing them into silence.
Ramaphosa has acknowledged the burglary but denies the alleged kidnapping and bribery, saying he reported the burglary to the police.
But the DA said it is asking the FBI to consider probing the source of the funds, how the cash was brought into the country and whether it was declared to authorities before the transactions at Ramaphosa's farm.
"A cash transaction within South Africa involving $4 million is deeply suspicious, and more so since the cash was then hidden in furniture, and its theft was investigated off the record and covered up," said Steenhuisen.