Johannesburg: South African President Thabo Mbeki has accepted the request of the ruling African National Congress (ANC) to resign, his office said on Saturday.

The ANC's decision to remove Mbeki, who was favoured by investors for his pro-business policies, came after years of infighting sparked by his 2005 firing of then deputy president Jacob Zuma in a corruption scandal.

Last week a judge dismissed graft charges against Zuma and suggested there had been high-level political involvement in the case. The ANC spurred Zuma militants within the executive to demand Mbeki's head.

The resignation may raise political instability in Africa's economic powerhouse 14 years after its transition from the end of white minority rule, although a smooth process to replace him, and reassurances on policy, will ease fears.

"Following the decision of the National Executive Committee of the African National Congress to recall President Thabo Mbeki, the president has obliged and will step down after all constitutional requirements have been met," the presidency said in a statement.

The decision must be ratified by parliament, which should be a formality, given the ANC's two-thirds majority.

The ANC's National Executive Committee, its top decision-making body, earlier decided to recall the president.

"After a long and difficult discussion the ANC decided to recall the president before his term of office expires," ANC secretary-general Gwede Mantashe said.

Frontrunner Zuma

Mbeki, who has ruled South Africa since taking over from Nelson Mandela in 1999, was due to leave office in 2009. He lost the leadership of the ANC to Zuma last year.

Zuma, popular with leftists within the party and with its trade union and communist party allies, is the frontrunner to succeed Mbeki.

It was unclear whether he would immediately step into the post. He would first have to be appointed to parliament and the cabinet.

Deputy President Phumzile Mlambo-Ngcuka might have assumed the presidency but she has signalled she will resign with Mbeki. Cabinet ministers and the speaker of parliament follow in the succession line.

It is generally expected that parliament, which is dominated by the ANC, will elect a new president within 30 days. Baleka Mbete, speaker of parliament and a Zuma loyalist, has been mentioned as the most likely one to lead the transition.

Mantashe said the ANC would ask Mbeki's cabinet ministers, including Fin-ance Minister Trevor Manuel - who is widely respected by markets - to remain in their positions in the transition period for the sake of stability.

Manuel's office said he would not step down - a decision that should calm some investors fears.

"If you have the continuity of the cabinet staying largely intact I would not expect a major market reaction," Citigroup strategist Leon Myburgh said.

"But you will have to see how individuals react as key decision-makers like Finance Minister Trevor Manuel will be key to how the market reacts."

Mbeki and Manuel have presided over the country's longest ever period of economic growth - a decade.

Mbeki's presidency finally ended after a heated debate within the ANC executive committee over his future in the wake of allegations he had meddled in the corruption case against Zuma.

Background: The key questions

How can the ANC push out Mbeki?

A South African president can be removed if two-thirds of parliament supports a vote outlining he was guilty of a serious violation of the constitution or laws.

He can also be deposed through a vote of no confidence which needs just a majority.

But the process is more simple if Mbeki resigns - parliament must then appoint a new president within 30 days. With the ANC's more-than-two-thirds majority in the National Assembly, this task should be a relatively easy process.

Why did the ANC ask him to step down?

Mbeki has been locked in a rivalry battle with ANC leader Jacob Zuma since 2005 when Zuma became embroiled in a corruption scandal. Mbeki fired Zuma as deputy president, enraging trade unions and rank-and-file ANC members.

The left was angry over Mbeki's pro-business policies and accused him of mounting a campaign to ruin Zuma's political career. Support from unions and members of the ANC youth wing helped Zuma defeat Mbeki for the ANC leadership late last year.

The infighting reached a climax last week when a High Court judge threw out graft charges against Zuma and suggested that high-level officials may have meddled in the case.

The prosecutors' decision to appeal the ruling further angered Zuma's supporters, who called for Mbeki to be fired.

Who will replace Mbeki?

According to the Constitution, Deputy President Phumzile Mlambo-Ngcuka could become president, but she has said she will step down should Mbeki be forced to leave office.

A cabinet minister or the speaker of the parliament could then be called on to lead a transitional government until an election is held. Zuma is widely expected to win the election and become president.

Will this worry foreign investors?

Uncertainty sparked by Mbeki's resignation is likely to weigh on investor sentiment and the rand currency. An early announcement on the way forward, however, could ease some of those concerns.

The fact that Mbeki has agreed not to fight the decision may calm some nerves. How his cabinet, and in particular, Finance Minister Trevor Manuel, react, is crucial. Manuel and Mbeki have presided over South Africa's longest period of economic growth.

A spokeswoman for Manuel said he would not resign. The ANC also said it wanted Mbeki's cabinet ministers to remain in their positions in the interests of national stability.

Mbeki's administration has been widely respected by markets and there are concerns that Zuma could tilt left as a result of his ties to trade unions and the small but influential communist party. Zuma has tried to reassure foreign investors that he will remain committed to growth and not shift away from current policies.

What about Mbeki's legacy?

Mbeki enjoyed the limelight briefly this month after brokering a Zimbabwean power-sharing deal that could end the southern African nation's deep political and economic crisis. But Mbeki's problems at home overshadowed the success.

Despite steering the country to prosperity, Mbeki has been accused of failing to dent poverty, unemployment and tackle the country's AIDS epidemic, one of the worst in the world. There is discontent among black South Africans who still lack electricity, water and other basic services. The country also has one of the world's highest rates of violent crime.

- Reuters