Nobel peace laureate, anti-apartheid icon and government gadfly Desmond Tutu was due to speak out Wednesday on 20 years of freedom in South Africa, the country he dubbed the "Rainbow Nation".
Anglican archbishop emeritus Tutu, 82, is still regarded as a moral beacon for South Africa in the mould of the first post-apartheid president Nelson Mandela, who led the country from 1994 to 1999.
But he has been openly critical of current President Jacob Zuma's graft-tainted administration.
With the ruling African National Congress now bereft of Mandela, who died in December, Tutu's comments at a news conference at St George's Cathedral in Cape Town ahead of elections on 7 May will be awaited with some apprehension by the government.
Although close to the ANC during the years of struggle against white-minority rule -- Mandela spent his first night as a free man after his release from prison in Tutu's home -- the archbishop said last year he would no longer vote for the ruling party.
"I didn't struggle in order to remove one set of those who thought they were tin gods and replace them with others who are tempted to think they are," he once said of South Africa's new leaders.
In 2011, the popular clergyman blasted Zuma's administration for being "worse than the apartheid government" after it failed to issue the Dalai Lama a visa to attend his 80th birthday -- vowing to pray for its downfall.
And he condemned a police "massacre" of 34 striking mineworkers in August 2012.
Next month's national elections are seen as a test of whether corruption, arrogance and enduring poverty after 20 years of ANC rule will hurt the party credited with ending apartheid.
The clergyman's refusal to vote for the ANC has been echoed in the run-up to the election by a group of former ANC stalwarts led by former intelligence minister and communist party member Ronnie Kasrils.
The group called last week for voters to choose one of the smaller opposition parties or spoil their ballots in protest against what they see as a betrayal of the ANC's principles.
The ANC is, however, expected to win the election easily -- riding on its "struggle" credentials -- but possibly with a reduced majority.