Now comes the hard part for France

PARIS - Sighs of relief and cheers for smart diplomacy were raised on August 11 when France finally coaxed the United States into backing a ceasefire deal for Lebanon at the UN Security Council.

But the feel-good surge has yielded to fears that the deal could unravel as France wrestles with the practicalities of implementing the key provision: deploying a UN peace force in southern Lebanon.

To secure the backing of Israel's ally for UN resolution 1701, France promised to lead efforts to boost an existing observer force, the UN Interim Force in Lebanon (Unifil), from 2000 troops to as many as 15,000.

Taking the field by November, the troops would work with around 15,000 Lebanese soldiers to restore peace after more than a month of fighting between Israeli forces and Hizbollah's Shiite militia.

But with the cessation of hostilities badly tested by fresh bursts of violence, the task of cobbling together the beefed-up Unifil have been hampered by reluctance from leading countries to commit troops, driven by concern over the force's exact role.

In France itself, signs of doubt surfaced abruptly last week, when at the last minute Defence Minister Michele Alliot-Marie stepped back from announcing, as had been expected, that France would send 3500 troops.

She gave no figure for France's commitment, but promised it would lead the UN force until February at least, provided the force was given a clear mandate - the UN must spell out what Unifil is expected to do, give it the means to intervene if need be as well as the right to defend itself.

While the UN hammers out these rules, France has sent only 200 personnel from an engineering division.

"You have to tell the troops why they are there. To support the Lebanese army, certainly, but to what extent? In what fields? Secondly, we also need to know what the material and judicial means at our disposal are," Alliot-Marie said.

"You can't send in men and tell them: 'Look at what is going on [but] you don't have the right to defend yourselves or shoot'."

Behind the scenes, Jacques Chirac is working the phones, pressing the leaders of friendly countries to get involved, French sources say.

The French president is especially targeting European Union (EU) countries as well as Turkey, which, as a Muslim country, would help project Unifil as a neutral rather than Western-biased force, they say. Talks are due to take place in Brussels on Wednesday on how to strengthen EU involvement.

So far, only two EU countries - Denmark and Germany - have promised contributions, but they amount to the safer option of ships rather than ground forces. Reports from Italy say Prime Minister Romano Prodi has promised as many as 3000 troops, provided the UN sorts out the rules of engagement.

Underpinning France's caution is the traumatic memory of past involvement in Lebanon.

In 1983, when France sent a large force to Lebanon - again to help secure an Israeli pullback - 58 French soldiers were killed in a suicide bombing of its barracks in Beirut.

That operation has been linked to Hizbollah, as was the subsequent kidnapping of French citizens and journalists in Beirut by Islamist groups. Today, Hizbollah is backed by Syria and Iran, both of which are locked in bitter diplomatic squabbles with France.

Thus, if Unifil lacked a clear mandate, the political support from the United Nations or the United States, or the means to intimidate those who attack them, it could become a sitting duck to provocative attacks. Strong and confident, Hizbollah is supposed to be removed as an armed force in southern Lebanon - a task that Israel itself failed to do.

The risk to Unifil is not exclusively from Hizbollah. Last month, four Unifil troops were killed in an Israeli airstrike that UN Secretary General Kofi Annan said was "apparently deliberate". Tim Williams, an analyst with the Royal United Services Institute for Defence and Security Studies, describes the new Unifil task as "a mission with significant complication" with a mandate that would lie somewhere between peacekeeping and peace enforcement and require excellent cooperation from its patchwork of units.

"A peacekeeping mission would be insufficient as the situation on the ground will demand the credible threat of force to secure the sanctity of the buffer zone and to deter aggression," writes Williams.

"Once in theatre, the success of the force will depend, in large part, on how effectively contributing countries can work alongside each other and whether robust 'rules of engagement' have been put in place."

Commentators in France wonder whether Chirac and his ambitious prime minister, Dominique de Villepin, have acted too hastily.

The political weekly Le Nouvel Observateur said: "After its diplomatic coup, France now faces concrete decisions and realises that the situation on the ground is riddled with uncertainties and contradictions."

The conservative daily Le Figaro, defending the Government's decision, commented: "This is a highly dangerous mission. If France volunteered to lead it's because it's an opportunity to make a comeback in the Middle East, where [France] has been sidelined by American unilateralism.

"However, the rest of the world cannot step aside and leave France holding the hot potato alone with help from a few Europeans and the inevitable blue helmets from Fiji."