But plans to change the constitution have yet to be approved by parliament, and there is a vigorous debate in South Africa about how land redistribution would work - and whether seizures could be economically damaging as they were in post-independence Zimbabwe.
President Cyril Ramaphosa wrote in the Financial Times today that "this is no land grab; nor is it an assault on the private ownership of property".
Earlier this year, Australian immigration minister Peter Dutton sparked a diplomatic row after he said that Canberra should give "special attention" to white South African farmers seeking asylum.
"We continue to encourage a peaceful and transparent public debate about what we consider to be a very important issue in South Africa".
There is no guarantee that expropriations will ultimately be limited to land; once momentum begins to build, it is probably inevitable that they will extend to other spheres of the economy.
State Department press secretary Heather Nauert told reporters that "the president asked the secretary to look closely at the current state of action in South Africa related to land reform".
He has also accused President Cyril Ramaphosa and the Democratic Alliance (DA) of colluding with AfriForum to sabotage plans to expropriate land without compensation.
Violent crime is a serious problem across South Africa and 47 farmers were killed in 2017-18, according to statistics from AgriSA, an association of agricultural associations.
"We would like to discourage those who are using this sensitive and emotive issue of land to divide us", he said. This has been deliberately driven by the government and ruling party, even though survey evidence has shown that land - particularly in the agrarian sense - is not a priority for South Africa's people.
"Reforming the land distribution and ownership will be good for South Africa", said independent political analyst Nic Borain.
"We'll not engage government about Trump, this is a government of cowards".
South Africa's rand currency dropped as much as 1.9 percent against the USA dollar following Trump's tweet, according to the Bloomberg news agency, ending four days of gains against the greenback.