The British Government's hope that the Kenyan Army can be a force for stability puts too much weight on that valuable but fragile institution. The danger is that if the Army takes on the burden of quelling violence that would likely follow the collapse of talks, the ethnic tensions that have torn Kenya apart will fracture the Army as well.

Resting so much hope on a military solution, even if a short-term one, avoids addressing the political problems since December's disputed election. If in two months ethnic clashes between rival tribes have led to the deaths of a thousand Kenyans and the flight of 600,000, then the Army, which bridges those same ethnic groups, will be under the same threat.

Yesterday Kofi Annan, the former United Nations Secretary-General, began personal talks with President Kibaki and Raila Odinga, the opposition leader, having given the two an ultimatum on Tuesday after weeks of fruitless talks. There were signs that his brinksmanship was working: Odinga called off mass street protests and Kibaki said publicly that he would create the prime minister's post which the opposition has been demanding.

Annan, widely seen outside Kenya as the best hope for brokering a solution, has been reluctant to call a formal end to the process. But Western diplomats say that despite some gestures from Kibaki, such as the offer of junior posts, they have seen no real acknowledgement of the other side's claim to have won the election or of the need to make concessions.

This week Lord Malloch-Brown, Foreign Office Minister for Africa, Asia and the UN, said: “the Kenyan military is by far the best option” for stopping violence if it flared up again. But although he acknowledged that “The question is, can it be brought in in a non-divisive way?”, that is a too explosive an option to dangle if the answer is not firmly yes.

The Army, about 20,000-strong, is one of the most professional institutions in Kenya, proud of its discipline and independence. It is respected for rising above the country's tribal divisions, and for including members from all sections of society. Many senior officers are, like Kibaki, from the traditionally dominant Kikuyu tribe.

But to put such weight on it risks fracturing it along ethnic lines, particularly as it would presumably remain under Kibaki's command. There are not many armies which could withstand the inevitable strain of bloody conflict in which their members sympathised with different sides. It has become a commonplace to say of Iraq that it was a mistake for the United States to disband the Iraqi Army but that rests on a blithe assumption that the force would have held together during years of ethnic persecution and killing.

The vanishing hope which Annan has been pursuing is that Kibaki can be persuaded to make concessions; that Odinga's supporters, despite their justifiable belief that they won the election, will accept them; and that a unity government could edge its way towards new elections.

At the moment, this course is out of reach. Kibaki has not, so far, bought the Annan compromise which would leave him in charge of defence and foreign policy but allow Odinga's team more purchase on domestic policy.

He has not, diplomats say, shown signs of accepting that he would have lost the election if it had not been for the widespread manipulation of votes. Businessmen warning that tourism will never recover have had little impact.

Facing a threat which could erupt again in days, Britain's plans are oddly conceptual, although ministers protest that they are spending hours sifting the options. Their preference is that if a deal remains impossible, that the neighbours, particularly Rwanda, become more involved. Britain could threaten to impose travel bans on key officials, which would hurt those with assets and children in school outside Kenya, Malloch-Brown said. But there is something of a gap between that threat and the kind of measures that might need to be imposed urgently if violence did erupt.

Annan is understandably reluctant to call it a day, for fear of triggering violence that will only make a bad situation worse. But Britain's invocation of the Kenyan Army is not a solution; it is a dangerous suggestion which emphasises that there are only ugly answers if Kibaki does not give way.

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