Regional leaders in southern Africa say Zimbabwe should form a unity government with MDC leader Morgan Tsvangirai as prime minister.
Following a meeting in South Africa, the 15-nation SADC grouping said that it had agreed that Mr Tsvangirai should be sworn in as prime minister by 11 February.
However, the opposition said it was disappointed with the outcome of the meeting, raising the possibility that deadlock would drag on as Zimbabweans face growing economic hardship.
It was its fifth attempt to secure a deal on forming a unity government.
All parties agreed control of Zimbabwe's hotly disputed Home Affairs Ministry should be divided between President Robert Mugabe's ZANU-PF party and the MDC for six months.
The issue has been a major obstacle to a final agreement.
The MDC said 'quite clearly the conclusions reached as reflected in the communiqué fall far short of our expectations'.
The party's national council will meet this weekend to define its position on the summit.
The signing of the power-sharing deal in September was seen as a chance to prevent an economic collapse that would add to the strain on neighbours already hosting millions of Zimbabweans who fled in search of work.
Others are escaping a cholera epidemic that has killed nearly 3,000 people and infected more than 56,000 since August - Africa's worst outbreak of the disease in 12 years.
