HARARE, Oct 8, 2008 (AFP) - Negotiators for Zimbabwe's President Robert Muagbe and his main rival Morgan Tsvangirai are going to meet again Wednesday in a bid to save a faltering power-sharing deal, an opposition spokesman said.

The two men agreed more than three weeks ago to form a unity government that would also include a splinter group of Tsvangirai's Movement for Democratic Change (MDC).

So far they have failed to agree on how to divide key ministries, leading the MDC to call for regional mediators to help break the impasse.

'Our negotiating team led by secretary general Tendai Biti has just been advised there is a consultative meeting,' MDC spokesman Nelson Chamisa told reporters.

'The way forward is going to be informed by what is going to happen at today's meeting.'

Under the deal, 84-year-old Mugabe would retain his position as head of state, after nearly three decades in power, while Tsvangirai took up the new post of prime minister.

Tsvangirai's MDC claims that Mugabe's ruling party wants to retain key posts -- believed to be the defence, home affairs, state security and finance ministries -- in violation of the pact.

Once a model African economy and regional breadbasket, Zimbabwe is now labouring under the world's highest inflation rate and crippling shortages of basic goods and food.