The US ambassador to South Africa accused the country of supplying arms to Russia.

JOHANNESBURG — The US ambassador to South Africa has accused the country’s government of supplying arms and ammunition to Russia during its invasion of Ukraine, escalating friction between the two countries over Russia and the war.

The ambassador, Reuben E. Brigety II, told reporters Thursday that Washington has reason to believe that a Russian ship that docked near Cape Town last December at a South African naval base, the Lady R, “uploaded weapons and ammunition.”

“We are convinced that weapons have been loaded on that ship and I will bet my life on the veracity of that claim,” Ambassador Brigety said, according to an excerpt of his exchange with the news media broadcast on South African news channel Newzroom Africa. .

During an exchange with lawmakers in parliament on Thursday, South Africa’s President Cyril Ramaphosa said only that the issue regarding the Lady R was “under investigation”.

Later on Thursday, the spokesman for Mr. had.

“It is therefore disappointing that the US ambassador has taken a counterproductive public position that undermines the understanding reached on the issue,” Magwenya said in a statement.

While the United States has called on its allies to condemn and isolate Russia, South African officials have refused to do so, citing the support the African National Congress, the governing party, received from the Soviet Union in the long struggle against apartheid and saying they took a neutral stance on the fighting in Ukraine.

However, US and other Western allies have said South Africa has not been neutral and has in fact supported Russia. Ambassador Brigety’s claim that Pretoria is supplying ammunition to Moscow is the sharpest diplomatic joke yet in an increasingly tense relationship. He made the remarks at a press conference in Pretoria that was open only to South African media.

Shortly after the ambassador’s remarks, South Africa’s currency, the rand, which had recently depreciated against the US dollar, continued to fall.

Ambassador Brigety’s remarks came about a week after he visited Washington with a delegation of South African officials, who held high-level talks with the Biden administration and lawmakers. The delegation, sent by Mr. Ramaphosa from South Africa, tried to iron out some differences between the countries.

Clayson Monyela, the head of public diplomacy at the South African Ministry of International Relations and Cooperation, criticized the ambassador’s statement in a post on Twitter. South African and US officials had discussed the issue of the Lady R, Mr Monyela wrote, and agreed on a course of action.

“Megaphone diplomacy was not part of that,” Mr Monyela wrote.

John Steenhuisen, the leader of the Democratic Alliance, South Africa’s main opposition party, called the ambassador’s statement “a chilling and deeply disturbing confirmation that President Cyril Ramaphosa and his government are actively involved in the Russian Federation’s war against Ukraine.”

Senator Jim Risch, the leading Republican on the Senate Foreign Relations Committee, called on the Biden administration to “reevaluate the scope and scale of our current involvement with the South African government.”

The US government has suggested retaliating against South Africa if it is found to have aided the Russian war effort or helped it evade sanctions. The United States has several options, including issuing sanctions and revoking trading privileges.

Lynsey Chutel contributed reporting.