President  Robert Mugabe and his Zanu-PF are plotting to oust South African president Jacob Zuma from his position as facilitator in Zimbabwe's political negotiations if he becomes chairman of the Southern African Development Community (SADC) troika of the organ on politics, defence and security co-operation on Thursday.

Zuma, the SADC facilitator on Zimbabwe, is set to assume the chairmanship of the troika at the regional grouping's annual summit, which starts on Wednesday in Luanda, Angola. This would give Zuma more power to tackle the Zimbabwe situation, on which he has of late become more firm.

Zuma mobilised regional leaders against Mugabe before the troika summit in Livingstone, Zambia, in March, where he issued a damning report on the political and security situation in Zimbabwe.

This angered Mugabe - who described the resolutions of the Livingstone summit as a "bombshell" - and forced him to attack Zuma and other leaders, saying they could not tell him what to do. The clashes led to a serious regional fallout, threatening the stability and cohesion of the SADC itself.

However, Zuma and other SADC leaders were not intimidated and further tackled Mugabe head-on at the extraordinary SADC summit in Sandton, Johannesburg, in June.

Informed SADC diplomats say Mugabe, now fed up with Zuma, is planning to stage a daring diplomatic coup against Zuma in Luanda. They say Mugabe and his strategists have been lobbying regional leaders to force Zuma to relinquish his role as facilitator if he becomes chairman of the troika on Thursday.

On Wednesday night Mugabe met with SADC chairman, President Hifikepunye Pohamba of Namibia, at State House in Windhoek to discuss the situation in Zimbabwe and the Zuma issue.

Mugabe was in Namibia for the meeting of former liberation struggle movements in the region where, insiders say, he lobbied intensely for support in Luanda.

Mugabe's strategists and loyalists have spent a week campaigning against Zuma through the state-controlled media. They have also engaged diplomats to build a coalition against him.

Insiders say Mugabe and Zanu-PF believe if Zuma becomes chairman of the troika he will have a "conflict of interest" on Zimbabwe.

They say it would be against the SADC "precedent" and "against principles of natural justice".

Zanu-PF officials say Mugabe is going to give Zuma options as part of the plot to oust him.

These include a proposal that SADC leaders must rule in Luanda on whether or not Zuma should remain as facilitator if he takes over as chairman of the troika.

If Zuma becomes chairman of the troika, then Mugabe wants him to recuse himself when the Zimbabwe issue comes before the troika.

The other option which Mugabe wants Zuma to consider is to postpone his assumption of the chairmanship until Zimbabwe is off the SADC agenda.

If all this fails, Mugabe wants a retired SADC president to be appointed as facilitator to replace Zuma. However, SADC executive secretary Tomaz Salomao said this week Zuma would remain facilitator and become chairman of the troika at the same time.

Salomao said it was untrue there was no precedent on that, as former South African president Thabo Mbeki had been facilitator and SADC chairman at the same time by sheer coincidence.

Zanu-PF officials reacted angrily, saying it was not Salomao's job to decide on such issues. They also said Salomao must stop "causing unnecessary confusion".

However, SADC diplomats told the Sunday Times that, besides what Salomao had pointed out on Mbeki, Mugabe was once involved in Lesotho and Swaziland situations during the 1990s while he was chairman of the troika.

But Mugabe's loyalists are unyielding. Zanu-PF politburo member and former Information Minister Jonathan Moyo said Zuma should choose between the two roles.

"To say President Zuma should execute the two duties is utter nonsense. He should choose one of the two hats. He cannot wear two because he does not have two heads," Moyo said.

"If they insist he should take the two responsibilities, they will be inviting the clear conclusion that there is a sinister agenda. That will create unnecessary tension within the facilitation team and the SADC itself."