In a recorded address, President Cyril Ramaphosa said the ruling ANC will "finalise a proposed amendment" allowing the move. He said the reform was "of critical importance" to the economy. Recent months have seen growing anger about the slow pace of land reform in South Africa.
The country's white minority is believed to have a disproportionate hold over land, with a few thousand white commercial farmers possessing the most fertile lands. However, critics fear expropriation could lead to land grabs, as happened in neighbouring Zimbabwe.
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In the video, Mr Ramaphosa said that a "proper reading" of the constitution allowed expropriation of land without compensation "in the public interest".
The ANC would go "through the parliamentary process" with the amendment. The country passed a law allowing expropriation in 2016. However, he said it had become "patently clear" that the people want the constitution to be "more explicit" on the matter.\
"This is the constitutional democracy that we fought for," the president said.
"We call on all South Africans to work with us on developing a social compact for economic inclusion, economic growth and jobs for all."
Around 10% of land in white ownership has been transferred to black owners since the end of apartheid, which is only a third of the ANC's target.