South Africa's main opposition party said a plan to join forces with another opposition group to challenge the ruling party in elections this year had collapsed, just five days after the leaders of the two groups held an upbeat news conference to announce they were merging their campaigns.
The sudden turnaround on Sunday reflected the deep divisions within opposition ranks in South Africa, which has been led by the African National Congress, the chief liberation movement during white racist rule, since Nelson Mandela was elected president in South Africa's first all-race elections in 1994.
Analysts expect the ruling party to win this year's elections, possibly with a smaller majority.
The Democratic Alliance party said in a statement that opposition leader Mamphela Ramphele had reneged on a deal to be its presidential candidate and to merge her smaller party with the Democratic Alliance.
Ramphele was the partner of Steve Biko, the Black Consciousness leader who died in police custody in 1977. She has been an activist, doctor, academic and World Bank executive.
"Doctor Ramphele has demonstrated - once and for all - that she cannot be trusted to see any project through to its conclusion. This is a great pity," Democratic Alliance leader Helen Zille said in the statement.
"It is not clear what her objective is, but whatever it is, it is not in the interests of the South African people," added Zille, who said Ramphele had insisted on going public last week with her acceptance of the offer to be presidential candidate for the Democratic Alliance.
Zille described Ramphele as a "long-time personal friend" and said she had sought to bring her into politics over many years.
Ramphele last year formed her own party, named Agang, or Build, in the Sesotho language, but struggled to gain political momentum. In a statement on Friday she said she remained leader of her party and that claims that she would be accepting membership in the Democratic Alliance were false.