JOHANNESBURG - MR THABO Mbeki, who presided over South Africa's longest period of economic growth, told the nation on Sunday that he has resigned as head of state, deepening the country's worst political crisis since apartheid.

Mr Mbeki, who took over fromn Mr Nelson Mandela as president in 1999, agreed on Saturday to accept the ruling ANC's request that he resign before the end of his term next year.

After an interim leadership is formed, Mr Mbeki's rival and African National Congress leader Jacob Zuma is all but certain to become president in the general election in 2009.

'I would like to take this opportunity to inform the nation that today I have handed a letter to the speaker of the national assembly...to tender my resignation from the high position of president of the Republic of South Africa,' said Mr Mbeki in a live speech on national broadcaster SABC.

The resignation will be effective from a date to be decided by parliament, said Mr Mbeki, looking subdued during his speech.

Militants in the ANC led the charge to oust Mr Mbeki about a week after a judge who threw out corruption charges against Mr Zuma suggested there was high-level political meddling in the case.

The fatal political blow came just after he scored his biggest foreign policy coup by mediating a power-sharing deal in Zimbabwe.

An acting president is expected to be announced on Monday, ANC treasurer-general Mathews Phosa said in a televised debate on SABC1. 'And he or she will announce the next Cabinet.'

Mr Phosa said the ANC wants the cabinet to remain, underscoring concerns that the departure of experienced, pro-Mbeki ministers could hurt the country.

'We want the Cabinet to stay. We are very happy if they stay and we do these things together,' he said.

South Africa's rand currency weakened nearly 1.5 per cent in electronic trading late on Sunday after Mr Mbeki announced his resignation.

Dangerous precedent
Mr Mbeki's brother, Moeletsi Mbeki, a political analyst who has been critical of Mr Mbeki's policies, was quoted in a newspaper as saying the ANC's ousting of Mr Mbeki was a 'recipe for civil war' that set a dangerous precedent.

President Mbeki has been credited with ensuring growth and attracting foreign investors to Africa's biggest economy. He was also instrumental in building a black middle class.

But critics and Mr Zuma's allies in trade unions and the Communist Party say Mr Mbeki was out of touch with millions of poor blacks.

South Africans, whose social and economic problems have been overshadowed by the fierce rivalry between Mr Mbeki and Mr Zuma, are bracing for a period of uncertainty. A deeply divided ANC is unlikely to ease their concerns over rampant crime, social ills and an Aids epidemic ravaging millions, analysts say.

Supporters of Mr Mbeki may split from the ANC and contest elections as a breakaway party in 2009, South Africa's Sunday Times said.

The move threatens to shatter the country's post-apartheid political landscape, dominated by the ANC.

A number of ministers have threatened to resign rather than serve in a Zuma-controlled government.

The Sunday Times said Defence Minister Mosiuoa Lekota, Deputy Defence Minister Mluleki George and other Mbeki loyalists are planning to start a new party and organisers will meet this week to discuss the move.

Finance Minister Trevor Manuel, widely respected by the market, will not resign, his office said on Saturday.

'Above all else, it is crucial that there is stability in government,' said opposition Democratic Alliance leader Helen Zille in a statement.

'An all out purge of ministers, particularly those that have carried out their jobs effectively, would have disastrous consequences for delivery. This must be avoided at all costs.'

Now that Mr Mbeki is out of the picture, Mr Zuma could come under stronger pressure from leftist allies in trade unions to ease poverty while he tries to win over the confidence of foreign investors who would not welcome more government spending.

'The main challenge is trying to end long-term uncertainty. If he can make progress in the fields of service delivery and unemployment and education it could go a long way,' said Mr Mike Davies, Middle East and Africa analyst at Eurasia Group. -- REUTERS