In 1994 almost 90% of the land was owned by white South Africans
South Africa will miss a 2014 deadline to redistribute a third of the country's farmland from white farmers to the black majority, officials say.
Land reform official Thozi Gwanya told the BBC the deadline had been pushed back to 2025 owing to a lack of funds.
He said more than $9.6bn (£5.8bn) was needed to buy the remaining land.
Influential ANC official Julius Malema has said land should be seized from white farmers refusing to sell - an option already rejected by ministers.
At the end of apartheid in 1994 almost 90% of land was owned by the white community, who made up less than 10% of the population.
Mr Gwanya said so far more than five million hectares have been distributed and about 20 million hectares remain to be bought.
He said the current economic crisis meant the government had been forced to postpone its redistribution plans.
But he said South Africa's constitution stipulated that land had to be bought - rather than seized - from the current landowners.
"It has never been our programme to just seize land," he told the BBC's Network Africa programme.
"Appropriation will be used in the event that there is no co-operation by the current landowners, so far we have got a very positive support from most of the white farmers."
But Mr Malema, the outspoken head of the ANC's youth wing, said the policy of asking landowners to sell up had failed.
He said they must be made a "non-negotiable offer" for the land.
"We will compensate but compensate with what we can afford - because anyway they stole it, they stole our land," he told the BBC.
The Confederation of South African Trade Unions (Cosatu) also said land redistribution was one of the main demands of the liberation struggle.
The powerful union bloc said rich taxpayers should pay more to ensure the deadline was met.
"An entire generation would have passed before we see this being implemented and that isn't good enough," said Cosatu's spokesman Patrick Craven.
"We're sitting on a social time-bomb," he said, adding that the recent township demonstrations over poor services were a warning.
"Those are linked to the land question. The fact that people are forced to move into cities to squatter camps... creates those kind of tensions.
"It would be far, far better if they could make a living in the rural areas - the main reason they can't is the skewed land ownership pattern which still exists in rural areas."
Land reform is a sensitive issue in South Africa and has been brought into sharp focus by the decline of agriculture in neighbouring Zimbabwe, where many white commercial farmers have been violently evicted.
Earlier this year, the government warned that it would take over any allocated land that was not being used effectively.
While last month, farmers' union Agri SA signed a deal to lease 200,000 hectares of land in the Republic of Congo as it said the government's land policy was forcing white farmers to seek land abroad.