President Thabo Mbeki's surprise proposal of a commission of inquiry to investigate alleged conspiracies against his former deputy, Jacob Zuma, has been described as his shrewdest move yet.

Analysts said Mbeki had characteristically played his cards close to his chest in the two months after the axing of Zuma and the escalating alliance tensions it caused. But as tensions threatened to spiral out of control this week he pulled out the unexpected "joker" card, contained in a letter delivered and read at around midnight during a 10-a-side tripartite alliance crisis meeting on the saga.

Commentators differ on Mbeki's motives, however, with some saying he was simply trying to calm tensions, while others believe the president was "calling the bluff" of those in the alliance who are demanding Zuma's reinstatement and the dropping of charges against him.

Mbeki said the commission was urgent and should also focus on supposed "hidden political agendas" and "expose and confront any and all factions that may exist within the ANC and the rest of the democratic movement". Indications are that the yet-to-be-considered proposal caught alliance partners, the Congress of SA Trade Unions (Cosatu) and the SA Communist Party (SACP), on the back foot at the meeting and raised their ire again when it was published on Friday.

SACP chairperson Blade Nzimande reacted with anger to the release of the letter, which he believed to be confidential, raising fears of another stand-off in the alliance, which seemed to pull back from the brink by finding some common ground during the marathon meeting in Johannesburg. The alliance partners jointly reaffirmed their support for Zuma.

Political scientist Steven Friedman said Mbeki had no choice but to act, as the allegations of a plot to destroy Zuma's chances of succeeding as president were increasingly affecting state institutions like the presidency and the Scorpions, at which some of the claims were directed.

Should such a commission be set up, Mbeki and Zuma are likely to be required to testify as Zuma himself alleged after being axed that there was a conspiracy against him and he might one day tell all.

Mbeki said he would appear before the commission if requested.

Analysts said Mbeki's response was typical in that his approach to problems was always to find a technical solution, even though alliance partners were calling for discussion.

"He had strategically withdrawn from the debate, which was to his credit, and now enters with a surprise rolling of the dice," said Idasa analyst Judith February. "Mbeki is always ready for political battle and people should not think he does not have the stomach for it."

KwaZulu-Natal-based commentator Aubrey Matshiqi allows for the possibility that Mbeki might be throwing down the gauntlet to sections of the alliance ahead of the 2007 congress, where his successor will be chosen, and that the withdrawal of one or more could not be ruled out.

"There is no way they will be able to prove a conspiracy," he said. "The commission might therefore intensify tensions in the alliance."

Asked whether the alliance partners were likely to accede to Mbeki's proposal, Matshiqi said: "They're damned if they don't and damned if they do. If they refuse it will prove they have something to be afraid of, and if they do, it will end like the Hefer Commission (which shredded allegations by Zuma supporters that former Scorpions boss Bulelani Ngcuka was a spy). Mbeki has called their bluff."

A number of legal experts cautioned that unlike the presidential-appointed judicial Hefer Commission, an alliance commission could not be headed by a judge and would not have search-and-seizure powers, but would have to rely on terms and references to be agreed upon by all parties; something that could cause further disagreement. In addition, Mbeki said it should be held in camera to protect identities and information.

But February said a closed inquiry would have little effect on perceptions among ordinary citizens who believe there is a conspiracy against Zuma.

"Mbeki's suggestion may water down or diffuse the tensions," she said. "However, in this case I am unsure how it could possibly work in practice."

Unresolved questions include who would drive the process, who would head the commission and how the inherently political process would be managed.

Although Mbeki stated that the inquiry should not jeopardise Zuma's trial, February fears that "ahead of the trial it would simply undermine the legal process and fairness at a time when we should be saying the rule of law is paramount".

Smuts Ngonyama, the ANC's spokesperson, said the suggestion would be discussed by the party secretariat and at a follow-up alliance meeting. It is understood this would be attended by Mbeki and Zuma.

Cosatu's general-secretary, Zwelinzima Vavi, said the federation's executive would study the idea on Wednesday. He pointed out two "dangers": the technocratic approach, and the security of those who would testify.

With acknowledgements to Christelle Terreblanche and The Sunday Independent.