Johannesburg  - Zimbabwe's Movement for Democratic Change (MDC) on Tuesday expressed regret that the party signed a power-sharing deal with President Robert Mugabe, without having first agreed on the composition of a unity government.

Speaking on South African radio about the three-week delay in the implementation of the landmark agreement, MDC spokesman Nelson Chamisa said he he thought the party's "big mistake" was to have signed a deal before the negotiations had been concluded.

Hopes for an end to Zimbabwe's economic and political crisis had been high when autocratic President Robert Mugabe signed a deal on September 15 to share power with his longtime rival Morgan Tsvangirai.

Under the deal brokered by former South African president Thabo Mbeki, Mugabe remains president with reduced powers and Tsvangirai becomes prime minister.

Three weeks later, fears that the deal could fall apart are mounting as Mugabe's Zanu-PF party and the MDC remain at loggerheads on how to share ministerial posts between them.

South Africa's ruling African National Congress leader Jacob Zuma on Tuesday urged the two sides to go the final mile.

Saying both sides might be tempted to hold out for the best possible deal for their party, Zuma said: "It must not be overdone."

Downplaying the impasse over the ministries, Zuma said: "They've gone through a lot of more difficult questions which they've resolved."

The bare-bones September agreement merely states that Zanu-PF is to get 15 ministries in a 31-ministry cabinet, Tsvangirai's MDC is to get 13 and a splinter MDC faction led by Arthur Mutambara gets three.

Despite widespread reports before the signing that the parties had agreed that the MDC would gain control of key ministries such as home affairs, which controls the police, and finance, and that Zanu-PF would retain defence, among others, the MDC says there was never any such agreement.

Early last week, Mugabe had said he expected the government to be finalized by the weekend and that only four ministries were still in contention. But later talks between the 84-year-old leader and Tsvangirai, 56, ended without a breakthrough.

Accusing Zanu-PF of wanting to retain its stranglehold on power, the MDC has referred the disagreement to the Southern African Development Community (SADC), which deployed Mbeki as a mediator.

"We are very clear that there hasn't been any progress," Chamisa said.

"There is a deadlock on the allocation of all key ministries and the allocation of governors," the MDC said later in a statement.

Since the agreement, Mbeki has been ousted by the Zuma-led ANC as South Africa's president.

SADC has endorsed him to remain on as mediator in Zimbabwe, but Mbeki has not yet returned try to shore up the deal, which is seen as crucial to salvaging Zimbabwe's battered economy.

Western governments are standing by to inject millions of dollars of aid and investment into Zimbabwe if an MDC-dominated government is installed. (dpa)