Leading article: France must honour its pledges and protect this fragile ceasefire

When France and the United States finalised the draft document that was to become UN Security Council resolution 1701, the agreement contained an unspoken deal. According to this, France would supply as many as 3,500 of the 15,000 blue-helmeted peacekeepers to be stationed in southern Lebanon; it would also stand ready to command the force. French confidence, it was anticipated, would encourage others to offer troops. At this point it seemed that the raising of the requisite force might be the least contentious aspect of the operation.

France was the obvious choice to assume the responsibilities this crucial mission would entail. Its long-standing ties with Lebanon gave it a unique familiarity with the region and the intricacies of its history. France's tradition of support for the Palestinian cause and its fierce opposition to the Iraq war gave it a credibility in the Muslim world that the British, in particular, lacked. Quite coincidentally, too, the French hold the command of Unifil - the existing UN force in southern Lebanon - which was seen as providing the core for the new, much larger and more proactive presence.

Regrettably, between last weekend and this, France seems to have lost its nerve. It now seems that a mere 200 French troops will be on offer - in addition to a similar number at present serving with Unifil - with perhaps another 2,000 or so on standby in the region but remaining under French command.

The potentially catastrophic result is that not only the peacekeeping operation, but the fragile ceasefire itself could be threatened. Without the expected lead from France, few other countries have yet come forward to offer significant numbers of troops. Some of those that have may, because of their foreign policy stance, raise objections from Israel. The desired international balance of the new force may prove hard to achieve.

French misgivings are not totally without foundation. The country's previous involvement in Lebanon ended in 1983, with the loss of 58 troops at the hands of a suicide bomber. Its experience of serving in the UN peacekeeping force in Bosnia was similarly costly. France is also right to want very specific rules of engagement. A force that is powerless to fulfil its mandate is as bad as no force at all. The Middle East in general, and this border in particular, offer as many examples of this sort of failure as anyone could require.

France has its own domestic political considerations, too. There will be hard-fought presidential and parliamentary elections in France next spring. The last thing President Chirac's ruling UMP needs is to be handicapped by an expensive and unpopular involvement abroad.

Yet France should think again. The new UN mission is clear. It is to enforce a buffer zone in southern Lebanon that should enhance the authority of the Lebanese government throughout the country and allay Israel's fears about its security. In one respect, it is an effort to tackle the same old problem that Unifil was deployed to resolve almost three decades ago.

The times, though, and the larger force envisaged, make this a very different proposition. And France surely has an obligation to help implement the Security Council Resolution, which it was prepared to sponsor. This was not just a piece of paper to be taken back to Paris as a diplomatic trophy. No other country is as well qualified or equipped for the operation that awaits.

There are risks and costs associated with every exercise in peacekeeping. This time the far greater risk is that the UN, and the international will it represents, will be discredited before the mission has even begun. The question then is whether the UN would ever be given another chance.