Secretary of State Mike Pompeo made the comments in an address in Ethiopia on the final day of an Africa visit largely aimed at countering China's influence on the continent of more than 1.2 billion people.
"Be wary of authoritarian regimes and their empty promises," he said, without naming names. "They breed corruption, dependency and instability."
Land is a sensitive issue in South Africa, which is one of the world's most unequal countries in part because of the legacy of the former racist system of apartheid that ended in 1994.
Some members of the ruling African National Congress and the populist opposition Economic Freedom Fighters have pressed for redistribution of land, arguing that it will help right past wrongs in which many black people were forced off their property.
Critics have warned against what happened in neighboring Zimbabwe, where sometimes violent land seizures from white farmers scared away some investors and deepened that once-prosperous country's economic collapse.
South African President Cyril Ramaphosa last week in his state of the nation address said the government plans to accelerate land redistribution this year. The government also plans to table an expropriation bill "that outlines the circumstances under which expropriation of land without compensation would be permissible," he said.
Ramaphosa has called land redistribution necessary to "redress a grave historical injustice." South Africa's government calls the dispossession of land by the 1913 Natives Land Act "apartheid's original sin," and one which continues to shape land ownership today.
The president also has attempted to soothe investors by saying there will be no chaotic or illegal land grabs, mindful of the need to not scare away business in a country with unemployment at a decade high of 29%.
This is not the first time the Trump administration has spoken out on South Africa's moves to redistribute land.
In 2018, President Donald Trump claimed that South Africa was seizing farms and that many farmers were being killed. In fact, farmers have been killed for more than 20 years in what is widely seen as part of the country's high crime rate, and experts say white farmers have not been the target.
The secretary of state is the first Cabinet official to visit Africa in 18 months. He also stopped in Senegal and Angola on a trip that seeks to reassert U.S. interests on a continent that many have accused the Trump administration of largely neglecting.
China, Africa's top trading partner for a decade now, is a major U.S. concern. Numerous other global powers have turned their focus to the continent of more than 1.2 billion people, many of them young.
Analysts have said a key task for Pompeo is countering the recent messaging out of Washington. New visa restrictions target Nigerians, Sudanese, Tanzanians and Eritreans, and the Pentagon is considering cutting the U.S. military presence on the continent even as Islamic extremism spikes in West Africa's Sahel region.
"Peace in Africa will be won by Africans," Pompeo told reporters Tuesday.