JOHANNESBURG -- Nelson Mandela's ANC, trying to coax black and white conservatives into South Africa's first all-race election, said Thursday it accepted their demand for international mediation over the new constitution.


Inkatha Freedom Party, or IFP, leader Mangosuthu Buthelezi, Mandela's main black rival, said earlier he was prepared to begin campaigning for the April election as soon as international mediation began.


With the latest deadline for registration expiring midnight Friday, Zulu leader Buthelezi also said that to be fair the April 26-28 election should be put back -- a demand that both the ANC and the government say will not be met.


But he added he did not wish to make an issue of the date.


"The national working committee agreed to the IFP proposal for international mediation to resolve outstanding matters," an ANC statement said after a meeting of its national working committee shadow cabinet.


Buthelezi, along with white separatist allies in the right-wing Freedom Alliance, has until now refused to take part in the elections on the grounds that the interim constitution under which they will be held is "fatally flawed."


The Freedom Alliance demands that the constitution provide water-tight guarantees for ethnic self-determination, including a separate white homeland for right-wing Afrikaners.


"If mediation has started, I would recommend to the central committee that we start campaigning," Buthelezi told reporters in Cape Town.


But he said the scheduled dates for the election were too soon and the vote should be put back. "It would only be fair, given that we haven't started campaigning yet," Buthelezi said


It was not clear what form mediation would take but the ANC proposed a joint working group should "address the specifics and agree upon mutually acceptable terms of reference."


White right-wing leader General Constand Viljoen has suggested mediation of the kind that brought Israel and the Palestine Liberation Organization to agreement.


The ANC statement said it would contact the IFP to discuss possible further meetings between Mandela and Buthelezi following talks they held Tuesday.


The meeting Tuesday, where Buthelezi asked for mediation, was the first between the two leaders since the IFP walked out of multiparty constitutional talks in mid-1993.


There was no immediate government comment on the ANC statement on mediation but President F.W. de Klerk said in parliament Wednesday there might not be enough time for it.


The Freedom Alliance, which met in Cape Town before the ANC statement, said the whole alliance supported the mediation demand.


Its threatened boycott of elections has raised fears of increasing political violence in the run-up to elections and afterward. About 14,000 people have been killed in township wars since de Klerk began dismantling apartheid four years ago.


Buthelezi and his white right allies have issued warnings of Bosnia-style civil war if their demands are not accommodated.


The Independent Electoral Commission, meanwhile, said results would not be announced until 48 hours after the polls closed on April 28. Commission officials said an estimated 22,710,000 people were eligible to vote.