An international force, possibly under the flag of the Organisation for Security and Co-operation in Europe, would then take possession of Kosovo and escort the refugees back.
Despite the deepening humanitarian catastrophe in Kosovo, and increasing impatience in Western public opinion, French sources say Nato governments have no intention of mounting a land invasion. In Nato circles the view is that international forces would not enter Kosovo until a "semi- permissive environment" had been achieved: in other words when the Serbs recognise that they are powerless to resist, even though they do not formally surrender.
Paris believes the alliance is weeks away from achieving the necessary degree of destruction of Serb infrastructure and military capability. But it would take even longer to assemble a ground force capable of invading Kosovo.
Such an invasion would cause even greater suffering to the Kosovars, French officials say, and would risk causing a wider conflict in the region.
More and more voices in France - as elsewhere - have been questioning this obsession with a limited war, in which all the risks are run by Kosovars and Serb civilians (and the Serb military), but not by alliance soldiers, and only in a limited way by alliance pilots.
The newspaper Le Mondesaid at the weekend that the attritional approach favoured by Nato was failing. But French officials insist that a combination of air power and diplomacy can still win the war. They say that there is no fundamental difference between the allies on the need for a diplomatic endgame. Paris has been the most insistent in calling for Russia to be kept in play; but all the allies accept that it is essential to avoid a Russian veto in the UN.
It is widely accepted, the French say, that the best solution would be a UN security council resolution, encapsulating the Rambouillet peace accord on Kosovo, which would be imposed de facto on Belgrade.
The French reject any suggestion that they are ready to break ranks to seek a diplomatic compromise. They say that France - which has 60 planes operational in the Balkans, 20 more than Britain - is committed to continuing the air war for as long as necessary.Reuse content