Zimbabwe's president has said a power-sharing deal which expires in four months' time should not be extended.
Robert Mugabe said the country should hold a referendum on a new constitution early in 2011 and then elections.
He said he was reluctant to renegotiate the unity deal as some events happening in the coalition were "foolish".
Mr Mugabe has been sharing power with rival Morgan Tsvangirai since last year, under a deal worked out after disputed 2008 elections.
"Some will say let us negotiate and give it another life. I am reluctant because part of the things that are happening [in the coalition] are foolish," Mr Mugabe said in comments broadcast on state television.
Prime Minister Tsvangirai last week said he was disgusted with Mr Mugabe and earlier this week suggested that Zimbabwe's ambassadors should not be recognised by foreign governments.
Under their accord, the two politicians agreed to draw up a new constitution followed by a referendum and then fresh elections.
But Mr Mugabe expressed frustration with constant wrangling within the coalition government, saying the lifespan of the political accord had reached its end.
"February next year, which is about four months to go, then it will have lived its full life and I do not know what is going to happen if we are not ready with a constitution," Mr Mugabe said.
Though the power-sharing pact does not specify how long the coalition government should last, it gives a 24-month timetable for the crafting of a new constitution seen as crucial for free and fair elections.
The process of reforming the existing constitution is already almost a year behind schedule, delayed by a lack of funds and disagreement over the composition of committees.
The BBC's Jonah Fisher, in Johannesburg, says that with Mr Mugabe's patience in coalition government clearly running thin, his statement has raised the possibility that Zimbabwe might vote without a new constitution in place.
The country has once more suspended its public outreach programme on a new constitution due to funding problems.
The public meetings were put on hold last month after a supporter of Mr Tsvangirai was killed during a meeting.
Mr Tsvangirai, who leads the Movement for Democratic Change, has accused the president of violating their agreement by unilaterally appointing ambassadors.
On Wednesday mediators from South Africa travelled to Harare to try to resolve the disagreement.