Zimbabwean President Robert Mugabe's threat to unilaterally form a government if opposition leader Morgan Tsvangirai continued to refuse to sign a power-sharing agreement was on hold Friday pending the resumption of talks Monday, political sources said Friday.

The sources said Mr. Mugabe issued that ultimatum in the belief that the talks would pick up again Thursday, and that Tsvangirai would again be presented with the draft agreement he has declined to sign saying that it does not give him sufficient powers as vice president.

Thursday's negotiations were canceled after Tsvangirai sent word to South African President Thabo Mbeki, mediator in the power-sharing talks under way since late July, that he would not be available to participate. Mr. Mbeki accordingly put off traveling to Harare until Monday.

Mbeki spokesman Mukoni Ratshitanga in Pretoria professed ignorance of his boss's expected trip to Harare. However, well-informed sources in both formations of the Movement for Democratic Change confirmed that Mr. Mbeki is expected.

Political analyst John Makumbe of the University of Zimbabwe told reporter Ntungamili Nkomo of VOA's Studio 7 for Zimbabwe that Mr. Mbeki's latest mission seems likely to be another futile attempt to forge an agreement between ZANU-PF and the MDC.

The talks have been hung up for some time on the issue of how executive powers should be shared by Mr. Mugabe as president and Tsvangirai as presumptive prime minister.

There were reports and statements this week – including by Tsvangirai himself to a South African radio station – suggesting that the MDC has become disillusioned with the power-sharing negotiation process and considers that it has run its course.

Tsvangirai was not immediately available to comment on such reports and statements attributed to him.

In Washington, a U.S. State Department spokesman on Thursday expressed Washington's opposition to the unilateral formation of a cabinet threatened by Mr. Mugabe. U.S. Deputy Secretary of State for African Affairs Jendayi Frazer told reporters in Swaziland Friday that if Mr. Mugabe follows through on his threat such a cabinet would be "a sham."

Asked if Washington would encourage the MDC to keep talking, State Department Deputy Spokesman Robert Wood said this that was a decision for the MDC to make. He said that the U.S. position is that any deal should reflect the will of the people as expressed in the presidential and general elections held on March 29.

Meanwhile, Tsvangirai's MDC formation was preparing to mark the ninth anniversary of the party's founding on Sunday at Mkoba Stadium in Gweru.

Although the opposition party has not arrived in power and remains embroiled in the power-sharing talks with Mr. Mugabe's long-ruling ZANU-PF, the combined MDC formations including the grouping led by Arthur Mutambara control a majority of seats in the lower house and in late August elected an MDC house speaker – a first since independence in 1980.

Organizing Secretary Elias Mudzuri of the Tsvangirai formation told reporter Carole Gombakomba that although the party has police clearance for the gathering it is not entirely clear it will be able to celebrate its anniversary without interference by state agents.

More news from VOA's Studio 7 for Zimbabwe...