Twenty years after announcing Nelson Mandela's release from prison, former South African president FW de Klerk on Tuesday commemorated the speech that began dismantling the apartheid regime.

De Klerk gave the closing address at a conference commemorating his February 2 1990 speech to Parliament, which called for a new democratic constitution, lifted the ban on dissident political parties and announced the release of all political prisoners, including Mandela.

Conference organisers said De Klerk's speech "opened the way to South Africa's constitutional transformation" and "announced the steps -- including the release of Mr Nelson Mandela -- which helped to open the way to the democratic transformation of South Africa".

"It really was a turning point of South African history," said Dave Steward, executive director of the FW de Klerk Foundation, which organised the conference and which the former president chairs.

Reflecting on De Klerk's speech, former African National Congress secretary general Cyril Ramaphosa told SAfm public radio on Tuesday: "He [De Klerk] was brave.

"Of all the apartheid rulers he was the braver one, who took the steps."

But Ramaphosa, who led the process of drafting the new Constitution, was also adamant that De Klerk's hand had been forced by pressure inside and outside the country for reforms.

"He had to do it," he said.

De Klerk, South Africa's president from 1989 to 1994, had been in office just five months when he delivered the historic speech. A one-time hard-liner in the pro-apartheid National Party, he would go down in South African history as the last apartheid president.

Mandela, for his part, was released nine days later -- on February 11 1990 -- ending his 27-year imprisonment. He would go on to become the country's first democratically elected leader.

The two shared the Nobel Peace Prize in 1993 for their work in ending the apartheid regime and building a new democratic South Africa.

But 20 years ago, De Klerk's speech was not an obvious political move, analysts told Agence France-Presse.

"For a white president to stand up and say, as De Klerk effectively did, that the South African government was willing to reconsider the principle of white minority rule was, at the time, an earth-shattering political development," said Laurence Caromba, a South African political analyst.

"It was a brave move. A very brave move in the face of potential disaster," said Paul Graham, executive director of the Institute for Democracy in Southern Africa.

At the time, South Africa's divisive political system had brought the nation to the brink of civil war. The economy was collapsing under the weight of international sanctions, and the country was "a steadily deteriorating pariah" internationally, Graham said.

With his speech, De Klerk, now 73, helped set in motion the country's transformation into a multiracial democracy and the sustained economic growth that followed the first all-race elections 16 years ago.

Organisers said the commemoration will both revisit De Klerk's speech and assess the country's progress in the two decades since.

Helen Zille, leader of the Democratic Alliance, will also deliver a keynote address on South Africa's development since 1990 -- a period that has seen the African National Congress rise to political dominance.

The country still faces many challenges 20 years on, including 30% unemployment, endemic crime, a faltering education system and the world's biggest divide between rich and poor.

"As we celebrate 20 years, I suspect there will be some reflection on whether we've made the best use we could have of the opportunities it provided," Graham said.

"There's a sense that it's a still-unfinished project, I suppose." -- Sapa-AFP, dpa