The move could increase tensions between South Africa and the United States as it moves to isolate Moscow over the war in Ukraine.
JOHANNESBURG — South African officials allowed a cargo plane targeted by U.S. sanctions for supporting Russia’s military efforts to land at an air force base near the capital, Pretoria, last week, a move that could further increase tensions with the United States.
U.S. officials previously said the plane has been known to ship weapons for Russia’s defense forces. South Africa’s Department of Defense said in a statement on Wednesday that the plane had been delivering diplomatic mail for the Russian Embassy. South African officials have declined to say precisely what was loaded on to and taken off the plane.
South Africa’s decision to let the aircraft land runs counter to American efforts to isolate Russia because of its invasion of Ukraine.
Although South Africa is not bound by the U.S. sanctions, the landing will “only serve to exacerbate the tense relations with the U.S.,” said Steven Gruzd, a researcher of Russia’s relationship with Africa at the South African Institute of International Affairs.
While South Africa has declared neutrality in the Russia-Ukraine war, he added, its foreign policy has increasingly leaned toward Russia.
“It’s always a choice,” Mr. Gruzd said. “South Africa is choosing to do this.”
A spokesman for the American Embassy in Pretoria declined to comment on the landing. The Russian Embassy also did not respond to a message sent to a spokesman.
The landing, reported on Thursday by Business Day, a South African news outlet, comes as the United States was already expressing concern about whether the government in Pretoria has been aiding Moscow during the war in Ukraine.
The United States has warned South Africa that it could face repercussions if it is found to have provided material support for Russia’s war. During a trip to South Africa in January, Treasury Secretary Janet Yellen said that the United States would respond “quickly and harshly” to governments that violate U.S. sanctions, a message that another top Treasury official echoed in a meeting with the South African delegation at last month’s World Bank and International Monetary Fund gathering.
Senator Jim Risch of Idaho, the ranking Republican on the Senate Foreign Relations Committee, said in a statement that allowing the plane to land was an affront to South Africa’s relationship with the United States.
“The South African people remain important partners of the United States, but we can no longer accept its government’s continued hostile acts against U.S. sovereign interests and must respond appropriately,” he said.
South Africa’s president, Cyril Ramaphosa, is already confronting a political storm over whether his government would fulfill an arrest warrant issued by the International Criminal Court for President Vladimir V. Putin if the Russian leader visits the country as part of a summit planned for August.
Flight radar records show the plane, an Ilyushin IL-76, originated at Russia’s Chkalovsky military airfield near Moscow on April 21 and made stops in the Middle East and Africa: Baghdad; Cairo; Damascus, Syria; Algiers; and Marrakesh, Morocco. It then headed to Nigeria’s capital, Abuja, and went on to Angola.
The aircraft then took off from Luanda, Angola, and landed at South Africa’s Waterkloof Air Force Base on April 24, the Defense Department said. (That day, flight records show an undisclosed stop, believed to be in South Africa.) The plane flew on to Harare, Zimbabwe, the next day.
The Russian Embassy had made a formal request to South Africa’s Foreign Ministry to let the plane land at the base, where diplomatic aircraft are allowed to travel, the Defense Department statement said.
It is not unusual for countries to deliver diplomatic correspondence by aircraft, but such deliveries are open to abuse, said Kobus Marais, a member of South Africa’s main opposition party, the Democratic Alliance. Mr. Marais questioned why the plane did not use a commercial airport nearby, which is more typical for offloading diplomatic bags, he said.
Diplomatic mail could be as small as a few envelopes or as a large as a container, but a defense analyst, Helmoed Heitman, said it was unusual for Russia to use a cargo aircraft to deliver packages to its embassy.
The flight plan and landing were most likely influenced by Western sanctions, said Mr. Heitman. “They might have had a suspicion that if they land at a commercial airport, they might get arrested,” he said.
The plane is owned Aviacon Zitotrans, a Russian company, and it was one of the aircraft from the company hit by sanctions by the U.S. Treasury Department in January as part of sweeping measures against Russian entities. Aviacon did not immediately respond to an email seeking comment.
The company has shipped military equipment around the world, including warheads and rockets, the Treasury Department said.
In December, a Russian container ship called the Lady R that is under U.S. sanctions was allowed to dock in South Africa’s naval port outside Cape Town. Allowing a commercial ship to use a naval facility raised concern among South Africans.
A U.S. official in South Africa said the American government believed that munitions and rocket propellant that Russia could use in the war might have been loaded onto the Russian tanker.
South Africa’s defense minister, Thandi Modise, said the ship was delivering “an old outstanding order for ammunition.”
