By James Macharia
JOHANNESBURG (Reuters) - South Africa's top court said on Tuesday it would consider whether a motion of no confidence against President Jacob Zuma should be taken by secret ballot, as pressure mounted on him to resign after a controversial cabinet reshuffle.
The rand extended its gains to 1 percent against the dollar after the announcement. Opposition parties said the motion would be more likely to succeed if held by secret ballot, allowing for anonymous dissent.
The ruling African National Congress party, which has a majority in parliament, has said it will vote against the motion, due on April 18.
Zuma, 74, has survived four previous no-confidence votes. But opponents led by the main opposition party Democratic Alliance (DA) believe a recent cabinet reshuffle that led to the dismissal of respected finance minister Pravin Gordhan may have angered enough ANC members to desert Zuma.
"We only need 65 to 70 people from the ANC, and the secret ballot can deliver the votes to remove Zuma," Bantu Holomisa, head of the smaller United Democratic Movement (UDM), told Reuters.
He earlier posted a court document on his Twitter feed showing the chief justice of the Constitutional Court had given the go-ahead for parties in the secret ballot case to give their written submissions by April 21 - days after the no-confidence vote is scheduled to take place.
The court document did not give a specific date for a hearing. Court officials were not available to comment.
"The debate on the no-confidence motion against Zuma will have to be postponed, we have written to the Speaker of parliament to push it back," Holomisa said.
"In the event that the Speaker fails to do so, we will seek a court order blocking the debate from going ahead."
DA leader Mmusi Maimane said he had also asked the Speaker to delay the vote until the case was determined.
The National Assembly is listed as a respondent in the case.
Parliament's Speaker Baleka Mbete, a top ANC official, has said the rules do not allow for the secret ballot and the ANC Chief Whip's office has rejected calls for one.
In 2015, the High Court dismissed an application which sought to force the National Assembly to vote on a motion of no confidence in Zuma by secret ballot.
Fitch and S&P Global Ratings last week downgraded South Africa to "junk", citing Gordhan's dismissal as one reason, and more than 60,000 people marched in South African cities on Friday to demand Zuma quit.
The DA, the ultra-left Economic Freedom Fighters, the UDM and other smaller parties plan a new protest march dubbed "National Day of Action" in the capital on Wednesday close to Zuma's offices, aimed at drumming up support for the no-confidence vote.
Zuma's office said the president would take part in his 75th birthday celebrations on Wednesday at a public venue in the township of Soweto, near the commercial hub of Johannesburg.
In a letter published in The Star newspaper, former president Thabo Mbeki urged lawmakers to act "as the voice of the people, not the voice of the political parties to which they might belong".
Mbeki was removed by the ANC as president in 2008 after Zuma became party leader the previous year.
Zuma has denied repeated allegations of corruption since winning power in 2009.
Nomura analyst Peter Attard Montalto said a secret ballot would not guarantee Zuma's removal because "even anti-Zuma MPs have real fear of the internal civil war that would result in the ANC". Zuma would still be president of the party.
(Writing by James Macharia; editing by Andrew Roche)