By Adam Mynott
BBC News, Nairobi
After the first few days of talks intended to find a solution to the Kenyan election crisis, the impressions emanating from the room where the Kenyan government and the opposition have been negotiating were generally quite favourable.
Mr Annan and the Panel of Eminent Africans know that time is crucial
Officials from the government Party of National Unity (PNU) and the opposition Orange Democratic Movement (ODM) were saying that "progress was being made".
But agreement was being found on straightforward issues; the items at top of the agenda drawn up by former UN Secretary General Kofi Annan were non-contentious.
It was almost as if he wanted to get the two sides into the habit of agreeing because he knows the difficult stuff lies ahead, and it will be best tackled by two sides who have at least been able to find common ground on something.
The agreement reached on Friday on an agenda for further talks - in conjunction with a programme to eliminate the appalling violence, which has killed 900 people and driven at least 250,000 from their homes - was billed as a breakthrough.
It was important, but "breakthrough" is probably pushing it a bit.
It did give the vital impression however that progress was being made, because Mr Annan and others in the Panel of Eminent Africans who are overseeing the mediation process realise that time cannot be allowed to drag.
This exercise has to be seen by the people of Kenya as a problem that is heading towards a solution. If not, violence and unrest will continue, or even get worse.
The agenda gave the negotiating parties about a fortnight from 29 January to come to agreement on sorting out the violence, finding a satisfactory humanitarian response for the tens of thousands living in misery and hunger, and tackling the "political issues".
A fourth agenda item of agreement on deep-seated institutional problems in Kenya was put in a separate category and given a time frame of a year.
Thousands of people have been displaced by the violence
The first two on the agenda have been relatively easy to come together on.
The "political issues", number three, centre around the events from the close of the polls in the presidential election at 1800 (1500 GMT) on the 27 December to 1700 (1400 GMT) on the evening of the 30 December when it was announced that Mwai Kibaki had won.
The two sides remain very far apart on this.
Mr Kibaki made it clear when he visited Ethiopia for the African Union Summit that he believes he won the election fairly and all the trouble since the election has been stirred up by the opposition.
Mr Odinga says he is in no doubt that he won the presidential poll and it was stolen from him by vote rigging.
The challenge for the negotiating team is in bringing the two men from these widely opposing positions to a point where they can agree on a way forward.
Both parties have said they are open to discussions but neither has indicated it is open to anything that the other might accept.
Of course, you do not go into a negotiating process putting all your cards on the table, but even allowing for a bit of flexibility it is very difficult to see a way out.
This has been the case in other intractable international crises as well, like Northern Ireland, and the very process of negotiation can lead to agreement.
But in the case of Kenya and its election it is hard to be optimistic.
No prime minister
I understand that Mr Annan and his team have rejected one possible solution; a re-run of the election, something that the opposition has said it might favour.
The fear is that another election would simply lead to more violence, and there would be no guarantee that either side would accept the outcome of a second presidential poll.
Mr Odinga would only be satisfied with a powerful executive position
The government says it is open to anything that "falls within the constitutional and legal framework of Kenya".
This is a very limiting set of conditions.
There is nothing contained in the existing constitution which would satisfy the opposition ODM, and the much repeated advice from government figures that "if ODM have a problem with the vote they should go to the courts" is equally unpalatable.
The opposition says that Kenya's judiciary has been filled with Kibaki-pliant men and women, and even if they were to get a fair hearing, the justice system in the country is so cumbersome and slow it would take an entire parliamentary term to get a decision.
So what remains as the only possible option is a form of power-sharing; and this is the area where Mr Annan and his team hope agreement might eventually be found.
At present, most executive power in Kenya is in the hands of the president.
Among other roles he appoints the cabinet, assembles and dissolves parliament, appoints all the parastatal heads and is the commander-in-chief of the military.
There is no prime minister in Kenya's constitutional make-up.
For Mr Odinga to agree on a "power-sharing deal" he must be given a powerful executive position.
He will not settle for anything else.
The government/PNU will only agree to give Mr Odinga a powerful post if they feel it will not undermine the authority of Mr Kibaki.