CAPE TOWN, South Africa (AP) — South African President Cyril Ramaphosa has appointed a judge to oversee an inquiry into allegations that the country supplied arms to Russia on a ship that docked secretly at a naval base in December.

The allegations were made this month by the United States’ ambassador to South Africa, who said he was sure that weapons and ammunition were loaded onto the Russian-flagged cargo ship Lady R when it docked at the Simon’s Town naval base near Cape Town late last year.

Ambassador Reuben Brigety indicated that the US had intelligence to sustain the allegation and he said he would bet his life on the accuracy of his claim that weapons were loaded onto the ship.

The Lady R container-carrying ship is under US sanctions for being tied to a company that has transported weapons to aid the Russian war effort in Ukraine.

South Africa has denied there was any government-sanctioned deal to provide weapons to Russia, although it hasn’t categorically ruled out that an unofficial transaction took place involving another entity.

Judge PMD Mojapelo, a former Supreme Court of Appeal judge, was appointed chairman of a three-member panel to investigate the incident, Ramaphosa’s office said in a statement on Sunday. A lawyer and a former minister of justice were also appointed.

The panel has six weeks to complete its investigations and another two weeks from then to provide a report to Ramaphosa, the president’s office said.

“The panel has been tasked to establish persons who were aware of the cargo ship’s arrival, and, if any, the contents to be off-loaded or loaded, the departure and destination of the cargo,” Ramaphosa’s office said.

Ramaphosa ordered the inquiry because of the seriousness of the allegations and “the impact of this matter on South Africa’s international relations,” his office said.

South Africa could be in breach of international law and its own laws regarding weapons sales if it is found to have supplied arms to Moscow for the war in Ukraine.

The incident has strained relations between the US and South Africa, which is Africa’s most developed economy and a key Western partner on the continent.

South African Defense Minister Thandi Modise has said the Lady R was visiting to deliver an ammunition shipment from Russia that was ordered by South Africa in 2018 but was delayed because of the COVID-19 pandemic.

Modise has refused to release cargo documents related to the visit by the Lady R after requests by opposition parties, saying they are classified. She said she will release them to the inquiry, though.