Zimbabwean and regional leaders met for 13 hours, but there was no deal
A summit of African leaders in Zimbabwe has failed to end the country's political deadlock.
The Southern African Development Community (Sadc) says a larger, regional summit should be held soon to try to reach a deal.
The key sticking point in Monday's talks was control of the home affairs ministry, which controls the police.
A power-sharing agreement signed six weeks ago has stalled over the allocation of cabinet posts.
President Robert Mugabe and his rival, Morgan Tsvangirai, held talks with former South African President Thabo Mbeki, and with regional leaders from Angola, Mozambique and Swaziland.
After 13 hours of talks, the group issued a statement calling for a summit of all 15 of Sadc's leaders "as a matter of urgency".
Asked what would happen if a full regional summit failed, Sadc's executive secretary, Tomaz Salamao said: "I can assure you that we will reach an agreement so that option is not relevant."
But Lovemore Madhuku, chairman of the National Constitutional Assembly lobby group, told the BBC's World Today programme that talks were proving "very inconclusive".
"I think [I] don't see them coming to an agreement now," he said. "It's now beginning to show what we have always suspected - that the two sides are irreconcilable."
Last month, Mr Mugabe and Mr Tsvangirai shook hands in Harare and signed what appeared to be an historic power-sharing agreement.
But attempts to form an inclusive government have run into serious trouble, BBC Southern Africa correspondent Peter Biles reports.
Mr Tsvangirai's Movement for Democratic Change says President Mugabe and his party, Zanu-PF, seem intent on controlling all the important ministries and sidelining the MDC.
Meanwhile, Zimbabwe is facing severe food shortages, both in the countryside and in the urban areas, and the country has the world's highest inflation rate.
UN Secretary General Ban Ki-moon on Monday said that it was "urgent to resolve the ongoing political impasse so that recovery can begin".
A statement issued in New York said he was concerned that "the humanitarian situation in the country may worsen in the course of 2008 and 2009".
Mr Tsvangirai has threatened to pull out of the deal, under which he would be named prime minister.
Mr Mugabe has allocated the key ministries of defence, justice and foreign affairs to Zanu-PF.
After four days of talks earlier this month, he reportedly agreed to let the MDC have the finance portfolio.
Last month's deal specifies that Zanu-PF should have 15 ministries, Mr Tsvangirai's MDC 13 and a breakaway MDC faction three.
But Zimbabwean journalist Brian Hungwe says the MDC also wants a share of provincial governors and ambassadors.
Although Mr Mbeki remains the facilitator of this tortuous process, some observers say he may have lost some of his influence since being forced to resign as South African president just days after brokering the deal.
The MDC has long criticised Mr Mbeki for his policy of "quiet diplomacy" towards Mr Mugabe and has previously called for him to be replaced.
"We respect Mbeki but quiet diplomacy has its limits if it leads to quiet approval of wrong things," Mr Tsvangirai said recently.