Zimbabwe's main opposition party has called for new elections, if power-sharing talks remain deadlocked.
New polls are the "only way forward", Movement for Democratic Change spokesman Nelson Chamisa told the BBC.
Neighbouring Botswana has also called for new elections, after a regional summit on Zimbabwe was postponed.
The MDC and the ruling Zanu-PF agreed to share power last month but they cannot agree on the details. A BBC reporter says there is a lack of trust.
The BBC's Jonah Fisher in Johannesburg says the atmosphere between the two parties is absolutely toxic.
A summit in Swaziland to discuss the deadlocked power-sharing agreement was postponed for a week after the MDC insisted that its leader Morgan Tsvangirai be granted a passport.
He even refused an offer to travel in Swazi King Mswati's private jet.
The Zimbabwe authorities gave him an emergency travel document - which the MDC said was an "insult".
But chief Zanu-PF negotiator Patrick Chinamasa blamed Mr Tsvangirai for the delay.
"Tsvangirai's failure to come to Swaziland seems to us to reflect his own reluctance or hesitancy to finalise and conclude discussions on the formation of an inclusive government," he told the state-owned Herald newspaper.
The Zimbabwean leadership seems to have failed to honour the agreement
Phando SkelemaniBotswana's foreign minister
Mr Chamisa said the talks were in a "very precarious position".
"People are suffering. The humanitarian situation... is dire. We need to respond to these challenges but we can't if we are locked up in endless negotiations," he told the BBC.
The power-sharing deal was supposed to resurrect the collapsing economy.
Zimbabwe has the world's highest inflation rate - 231,000,000% - and donors say half the population will soon need food aid.
"We need to go to elections, if this dialogue process fails," Mr Chamisa said.
Mr Tsvangirai has agreed to become prime minister, working with President Robert Mugabe but the two men cannot agree on the division of cabinet posts.
Mr Mugabe has allocated the key posts to his Zanu-PF party, prompting Mr Tsvangirai to threaten to pull out of the deal.
Talks will now resume in the Zimbabwean capital, Harare, on 27 October, according to a statement from the regional Southern African Development Community (Sadc), which oversaw the power-sharing deal.
But Botswana adopted a different line and called for new elections.
"The Zimbabwean leadership seems to have failed to honour the agreement," Foreign Minister Phando Skelemani told the BBC.
The BBC's Africa analyst Martin Plaut says the statement carries an air of desperation. Given the bloodshed during the last presidential election it is hard to see how this could be undertaken without foreign troops or a terrible loss of life, he says.
President Mugabe has allocated the main ministries, including defence, home, foreign affairs, and justice to Zanu-PF.
As well as finance, the MDC also insisted it should have home affairs - and control of the police - if Zanu-PF had defence.
The MDC accused the security services of taking part in violent attacks on its supporters before June's presidential run-off election.
Reports on Friday suggested that Mr Mugabe might have agreed to let the MDC take the key post of finance minister, but that he would not give it home affairs.
Finance is one of the most crucial posts, as Zimbabweans hope the power-sharing deal will lead to action to tackle the economic crisis.
Donors have promised to help finance a recovery plan but they are unlikely to release funds if a Zanu-PF minister is in charge.
Some two million people need food aid and non-governmental agencies warn that figure could double within the next few months.