The question will be whether Mr de Klerk and Mr Mandela can offer Chief Buthelezi, the Inkatha leader, and the Zulu king enough of a stake in the new political order to persuade them to call on their supporters to stop the terror campaign against Zulus who wish to vote in this month's elections.
The meeting will bring together the four leaders for the first time. It comes at the end of a week which has seen the death toll in Natal/KwaZulu exceed 120. The imposition of a state of emergency in the area a week ago has not reduced the killings - there were 300 in the whole of March - but it was only yesterday that the South African Defence Force started deploying troops in significant numbers around the more violent areas.
The hope of the government, the ANC and the smaller parties contesting the 27 April elections is that further army reinforcements expected in the coming days will help bring Natal/KwaZulu sufficiently under control to allow for acceptably free and fair elections.
One indication that the iron fist approach is having some effect was provided earlier this week by the decision of KwaZulu's one-party Inkatha government to shut down its paramilitary training camps. Had they not, the threat was there that the army - empowered by the emergency regulations - would have done it for them.
When the two most powerful commoners in South African politics sit down at the negotiating table this morning the first thing they will try to gauge is what exactly King Goodwill and his nephew, prime minister and prince of the Zulu royal house, really want.
Chief Buthelezi had initially demanded a federal system of government in Natal/KwaZulu so autonomous it would have amounted virtually to the province seceding from the rest of South Africa. When this failed he wrapped himself in the flag of Zulu nationalism, resurrected King Goodwill after two decades in the political wilderness and, through the king, issued a call for the transformation of Natal/KwaZulu into an independent Zulu kingdom. What will emerge today is whether these have been bottom- line positions or opening negotiating gambits.
Mr de Klerk and Mr Mandela find themselves at these talks on the same side, sharing the same objectives. The peace offering they shall be putting before the Zulu leaders will revolve around what a government official called 'the king thing'. Their proposal is designed to satisfy the demand for a Zulu kingdom, but stops well short of independence.
According to government and ANC insiders, a Zulu monarchy would be entrenched in the constitution. The king, his prime minister and his princes would not be able to undermine the functions of the elected provincial - much less the national - government but they would have powers over tribal affairs, such as the resolution of land disputes and, most important, they would receive a handsome budget from central government.
The next issue on the agenda will be the elections. Chief Buthelezi will be demanding a postponement of the election date. Neither Mr Mandela nor Mr de Klerk are prepared to accept this.
The Independent Electoral Commission (IEC) - the body supervising the elections - does not contemplate a postponement either. An IEC report this week said it would be impossible to hold free and fair elections in KwaZulu 'in the present climate'. But the IEC chairman, Judge Johan Kriegler, said this did not mean elections would not take place in the rest of Natal. Furthermore, all available measures would be taken to ensure as many people as possible in KwaZulu would be able to vote.
'We can't let the spoilers spoil the election for those who don't want to spoil,' Judge Kriegler said.
One solution would be to register Inkatha on the election list. But it is more likely that the problem will remain unresolved and it will be left to the army to put up a sufficient show of strength to persuade people in KwaZulu it is safe to vote, thereby spoiling the ambitions of the spoilers.