A parliamentary vote of no confidence in South African President Jacob Zuma will be held by secret ballot, it was announced on Monday, a move that could encourage some ANC lawmakers to vote to oust him.
The vote, scheduled for Tuesday, has become a test of African National Congress (ANC) unity as senior party figures have been increasingly critical of their leader, but it is unlikely to succeed in toppling Zuma.
"Voting on the motion of no confidence in the president... will be by secret ballot," parliamentary Speaker Baleka Mbete announced, in a decision that took many analysts by surprise.
The president, who came to power in 2009, has been implicated in multiple corruption scandals, while the country's economy has fallen into recession and unemployment has risen to record levels.
The 75-year-old is due to step down as head of the ANC in December, and as president before the 2019 general election -- lessening pressure for his party to seek imminent change.
The vote has been subject to a long legal battle waged by opposition parties, with the Constitutional Court ruling that a secret ballot was permissible.
"It's a surprising but strategic move," independent analyst Judith February told AFP.
"Zuma is likely to remain even if a few MPs vote against him. I would be very surprised if Zuma goes by this process.
"The decision takes the wind out of the sails of opposition as well as civil society marches and activism around this issue."
'Larceny on a grand scale'  
Protests by pro- and anti-Zuma groups are planned in Cape Town, home of the South African parliament, later on Monday and on Tuesday.
The main opposition Democratic Alliance party said the vote was "an opportunity for us all to stand up to corruption and get rid of President Zuma and his cabinet."
A group of ANC veterans from the anti-apartheid struggle has also called for MPs to vote against Zuma, who was himself imprisoned with Nelson Mandela on Robben Island under white-minority rule.
South Africa is "witness to larceny on a grand scale, leaving the country not only impoverished, but also increasingly in the hands of criminalised and compromised governance," the veterans said in a statement before Mbete's announcement.
"The motion of no-confidence in President Jacob Zuma is an inevitable outcome of the myriad scandals in which he has regrettably embroiled himself and his office," they added.
The ANC has fought back, saying last week it expects its lawmakers to back the president.
Party chief whip Jackson Mthembu said ousting Zuma would "have disastrous consequences that can only have a negative impact on the people of South Africa".
But he acknowledged recent criticism of the ANC, and the impact of a cabinet reshuffle in March when respected finance minister Pravin Gordhan was replaced with a Zuma loyalist.
Gordhan's sacking led to a string of downgrades to South Africa's credit rating as well as causing the rand currency to tumble.
Public support for the ANC, which swept to power under Mandela in the first non-racial elections in 1994, slipped to 55% in last year's local polls -- its worst-ever result.