South Africa is moving ahead with implementation of the National Health Insurance (NHI) bill, President Cyril Ramaphosa said, despite strong opposition from within and outside government.

The NHI aims to provide universal coverage through a major overhaul of South Africa's two-tier system. Ramaphosa signed the bill right before the May election in which his African National Congress lost its parliamentary majority.

"We have highlighted the social and economic value of affordable, accessible, quality health care that is available equally to all South Africans," Ramaphosa said in a speech on Tuesday evening, at the closing of an ANC policy meeting.

"We will therefore proceed with the implementation of the National Health Insurance."

Speaking earlier on Tuesday, Health Minister Aaron Motsoaledi said that the section of the bill which outlines transitional mechanisms would be implemented "immediately".

This includes setting up advisory committees and amending other health-related laws to be in line with the NHI.

The legislation will gradually limit the role of private insurance in South Africa, create a new public fund to provide free access for citizens, and set the fees and prices that private healthcare suppliers can charge for NHI-funded benefits.

Supporters call it a generational change to reverse inequality dating to the apartheid era. But opponents, including big local health insurers, say the proposed funding model won't work.

Motsoaledi said he would listen to concerns from stakeholders and help people understand the NHI.

"The real poor people who are (set to be) beneficiaries haven't spoken," he said. "Nobody's carrying their voice."

One opponent of the bill is the pro-business Democratic Alliance (DA) party, which formerly led the opposition and has now joined the ANC in government.

DA leader John Steenhuisen said last month that the NHI continued to be a sticking point for the coalition government and that discussions on it would continue.

Motsoaledi said the bill would be implemented in phases over years and acknowledged that legal challenges could delay its roll-out.