Plans by South Africa's ruling African National Congress (ANC) to change the constitution to allow the expropriation of land without compensation have unnerved investors, a senior World Bank group executive said on Wednesday.

President Cyril Ramaphosa's party has made the acceleration of land redistribution a key issue ahead of 2019 elections, while pledging to carry out land reform in a way that does not threaten food security.

Most private land remains in the hands of the white minority more than two decades after the end of apartheid, making it a vivid symbol of wider disparities.

"If you create uncertainty of some aspects of your environment, and land tenure is one of them, that is one aspect that investors will be looking at," Sérgio Pimenta, the vice president for the Middle East and Africa at the International Finance Corporation (IFC), the World Bank's private investment arm, told Reuters.

"What investors are looking for is certainty," he said on the sidelines of a meeting between the World Bank and member countries in Livingstone, a town located in Zambia south of the capital Lusaka.

"The land issue is a complex issue," he said. "Whatever the solution the government is looking at, creating an environment that is reliable, that is certain, is important."

Public hearings on land redistribution were held earlier this year across South Africa, attracting large crowds and often emotional testimony.

A parliamentary committee will consider that testimony and other contributions before recommending whether or not to change the constitution to allow land to be expropriated without compensation.

Pimenta said South Africa's long-term economic outlook was positive. The Bank had invested about $2-billion through the IFC over the last 5 to 6 years, he said.

Africa's most industrialised economy is struggling with ballooning debt that risks pushing its sovereign credit ratings deeper into "junk" territory. Other problems include cash-strapped State firms and a stubbornly high unemployment rate.