South Africans will vote in a general election on April 22 in what is expected to be the most closely contested poll since apartheid ended in 1994.
South Africa's ruling ANC, in power since then, is widely seen winning the election but faces an unprecedented challenge from the new Congress of the People (COPE) party.
COPE, formed by ANC dissidents in December, may gain enough votes to deny the ANC a two-thirds parliamentary majority which enables the ruling party to easily push through changes to the Constitution.
South African President Kgalema Motlanthe said the formal proclamation of the election day would take place later. The government is opposing legal action from a smaller political party seeking voting rights for South Africans abroad.
The High Court ruling has been referred to the Constitutional Court, the country's highest court.
But analysts said the legal challenge is unlikely to delay the election.
"I suspect the government has taken the view that what needs to be done is so minor that it would probably be done by April 22. It is quite enough time. I suspect they have already put a few things in motion to sort it out and I do not think they would want this to be dragged through the courts," said Thabo Rapoo, executive director at the Centre for Policy Studies.
ANC leader Jacob Zuma, who enjoys the support of trade unions and the Communist Party, is expected to become President despite revived graft charges, creating political uncertainty in Africa's biggest economy.
Several ex-ANC heavyweights have joined COPE and South Africa's former Deputy President, Phumzile Mlambo-Ngcuka, is preparing to leave the ANC and join the breakaway party, according to local media.
Mr Mlambo-Ngcuka was Deputy President under former President Thabo Mbeki until he was ousted as state President by the ANC last September.
A flare-up of political violence in the Zulu heartland of KwaZulu-Natal has also raised fears that the 2009 elections could be marked by violence.
Violence erupted earlier this month after the ANC held a rally in northern Zululand, a key electoral area for the party and the Inkatha Freedom Party, the second largest opposition party. ANC buses were stoned and an ANC MP wounded in a shooting.