Dissident members of South Africa's governing African National Congress are gathering in Johannesburg to discuss the formation of a breakaway movement.
More than 4,000 people are expected to attend the two-day convention to draft policies for the new party, expected to challenge the ANC in polls next year.
The bitter ANC split followed last month's swift forced resignation of President Thabo Mbeki.
Police have tightened security around the venue to prevent any violence.
This weekend's meeting will bring together the ANC dissidents as well as some of the country's opposition parties, which now see a political realignment on the horizon.
The new party, which does not yet even have a name, is due to be officially launched in December, officials of the movement said.
The convention should provide a clearer indication of the precise challenge the ANC is now facing, says the BBC's Peter Biles in Johannesburg.
The oldest party on the African continent is facing its biggest crisis in nearly 50 years, according to our correspondent.
Mr Zuma says the party is unfazed by the upheaval of recent weeks but with a general election just months away, analysts believe the ANC's troubles may affect its campaign.
The infighting stems from a power struggle between Mr Mbeki and Jacob Zuma, who defeated Mr Mbeki to become party leader last December.
Mr Mbeki stood down in September after a judge suggested he may have interfered in the prosecution of Mr Zuma on corruption charges. Mr Mbeki strongly denies the claim.
His ousting led ex-defence minister Mosiuoa Lekota and other loyalists to quit the ANC in protest.
Mr Lekota, a former ANC chairman and leader of the breakaway movement, officially resigned from the party on Friday.
The disaffected ANC members accuse the party of undermining South Africa's young democracy.
The political schism marks a dramatic shake-up in a country where the ANC has dominated political life since the end of white-minority rule in 1994.
The ANC won more than two-thirds of votes in the last election and controls a strong majority in parliament.