"You can't have it dragging on forever. The sooner the matter is concluded the better," Mbeki told reporters in Pretoria.

Zuma's office was plunged into crisis on Sunday after the local Sunday Times newspaper published questions posed to him by South Africa's elite Scorpions detective unit about his relationship with Thomson-CSF of France (now known as Thales), which is supplying equipment to the armed forces, and his financial interests since 1994.

The newspaper said it was alleged that Zuma tried to solicit 500,000 rand (68,000 dollars/59,000 euros) from Thomson-CSF. In return Zuma allegedly offered to protect the company during subsequent investigations.

South Africa's arms deal has been plagued by allegations of corruption ever since 1999 when a member of parliament called for an investigation into claims that senior politicians had taken kickbacks.

Mbeki expressed concern about the allegations and counter-accusations on the issue reported in the media over the past few days.

"But I suppose the prosecuting authorities would not have said what they have said, or done what they are doing, if they didn't think they had just cause to do it," Mbeki said.

"And I would imagine the deputy president wouldn't make the statements he is making unless he was convinced that he has just cause to say the things he are saying.

"The law-enforcement agencies must do their work as they think is right. Indeed, if there is any course to charge any person, of course they must proceed and do so," he said.

In 1999, in contrast, Mbeki's office issued a statement that "the presidency rejects any insinuation that Deputy President Zuma is implicated in shady arms deals".

Zuma, 61, has a high profile in Africa as a leading negotiator on peace deals in Burundi and the Democratic Republic of Congo, and he is also credited with making peace between the governing African National Congress (ANC) and the Zulu-based Inkatha Freedom Party as apartheid ended in 1994.

He questioned the motives behind the leaking of the questions, saying: "this is a serious breach of confidentiality" after the report was published on Sunday.

He added that he was not guilty of any wrongdoing and urged those who believed they had a case against him to prove it in court.

Zuma, who is also deputy president of the ANC, remains high on the list of possible successors to Mbeki, who is due to begin his second and final five-year term as president next year, even though the deputy president declared in 2001 that he had no interest in the post.

Those close to Zuma are speculating that the campaign against him is linked to the elections.

Sipho Ngwema, the spokesman for the Scorpions, has said that most of the questions to Zuma related to his relationship with his financial adviser Schabir Shaik, who is also under investigation regarding the arms deal.

Other information Zuma has been asked to provide relates to financial benefits he received from various sources, including former president Nelson Mandela, his debts and all expenses he paid on behalf of the ANC since 1994.

Zuma's diaries, official and private travel plans and itineraries since 1995 have also been asked for.

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