HARARE, Oct 7, 2008 (AFP) - Zimbabwe's political rivals failed to reach an agreement on forming a unity government during their latest talks Tuesday, leaving a power-sharing accord in doubt, an opposition spokesman said.

'Our negotiating teams met for two hours today, but sadly, we are still in different worlds in a fundamental way,' Nelson Chamisa told AFP.

President Robert Mugabe and Morgan Tsvangirai of the opposition Movement for Democratic Change (MDC) signed signed a power-sharing agreement more than three weeks ago after contested presidential and parliamentary elections.

But they have since been at loggerheads over the make up of the new government.

'We feel that we should have an equal sharing of key positions and (the ruling) ZANU-PF feel they need to take all important ministries. That is the cause of the deadlock,' Chamisa said.

'Our position is not about power but the opportunity to change the lives of the people, and we can't make any impact when we have small minstries. ZANU-PF wants to maintain the status quo by holding on to key ministries,' Chamisa said.

'They continue to play games, yet they know people are hungry and are anxious for change.'

The MDC has called for regional mediators to help break the impasse, but Mugabe's party has insisted that no outside intervention is needed.

The deal was brokered by former South African president Thabo Mbeki. He has agreed to return to the negotiations if he is needed.

Under the deal, 84-year-old Mugabe retained his position as head of state, after nearly three decades in power, while Tsvangirai assumed 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.