Former UN chief Kofi Annan has said rival parties in Kenya appear unable to resolve their differences, despite weeks of talks between the two sides.
Mr Annan urged President Mwai Kibaki and opposition leader Raila Odinga to reach a settlement after separate meetings with the pair.
They disagree on the powers granted to a proposed new post of prime minister.
The disputed re-election of President Kibaki in December has unleashed a wave of political and ethnic violence.
Police now say at least 1,500 people have been killed in the past two months.
Mr Annan has been in Kenya for more than a month trying to resolve the crisis - the longest period he has spent on any conflict resolution.
Frustration.
The former UN secretary general met both Mr Odinga and Mr Kibaki on Monday, to urge them to reach agreement.
Afterwards he said the mediation team had "done its work - I'm now asking the party leaders to do theirs".
The BBC's Adam Mynott in Nairobi says Mr Annan is clearly frustrated by the lack of progress.
A member of the mediation team told our correspondent that the problem lies with the government, which is unwilling to confront the reality of sharing power.
Mr Annan is reported to have said that he feels like a prisoner of peace - unable to achieve an agreement but unable to leave Kenya.
Mr Odinga's ODM party has threatened to relaunch mass protests on Thursday if a political deal is not reached, while a lawyers' group says it wants to see a resolution by the end of the week.
The ODM and government negotiators were due to fine-tune an agreement that would usher in a new power-sharing arrangement.
The incoming African Union commission chairman, Jean Ping, who held talks with President Kibaki and Mr Annan, hinted last week that a deal would be announced early this week.
Both parties have agreed in principle on the creation of a prime minister's position, which would be taken by Mr Odinga.
As well as how to divide powers between a prime minister and a president, the rivals are also split on sharing on cabinet positions and the possibility of a new election if the coalition collapses.
Source: MJFM
