Deployment of the force, which could number up to 50,000 troops, will be unprecedented in the history of the alliance. At a meeting of Nato foreign ministers next week in Williamsburg, Virginia, the allies will be asked by the US to state how many troops they are prepared to contribute and how much they are ready to pay.
The US peace-negotiating team has called for the operation to be prepared urgently on the grounds that all sides could be ready to sign up to the new peace map before the end of October.
Reporting to Nato leaders in Brussels yesterday on Tuesday's New York peace deal, Wesley Clarke, military adviser to Richard Holbrooke, the US envoy, spoke in "highly optimistic terms", according to officials. If the final signing can take place as soon as the US hopes, Mr Holbrooke and his team believe the Nato force must be deployed "within days", to prove to the warring parties and the people of Bosnia, Croatia and Serbia that the war really is over.
The US has stipulated that the Nato-led force, which is expected to include troops from Russia and other non-Nato countries, will stay in the region for a year, Nato sources said. A strict deadline is essential if the US Congress is to be persuaded to approve the sending of troops. The force will then be replaced by UN peace-keepers.
However, as the time-table for the deployment starts ticking, fears are mounting that the operation could yet flounder over how to involve Russian forces.
It is seen as imperative by Nato that Russian forces must be deployed alongside those of the alliance and other states, if the peace-enforcement operation is to have credibility among all the former Yugoslav republics. The US is expected to send up to 23,000 troops, and Britain has said it would send 15,000. France is expected to match the British deployment.
President Boris Yeltsin, however, has insisted that if Russian forces are deployed, they cannot come under Nato command, and Russia must have a joint share in the command and control structure.
Given that the peace-enforcement operation must first be agreed by the UN Security Council - on which Russia holds a permanent seat - President Yeltsin appears to have a strong bargaining position.
However, the US has rejected Russian calls for a joint share in the command and control of the operation. Instead, according to Nato sources in Brussels, Mr Holbrooke has offered Russia a "consultative role" in the military decision-making.
At Williamsburg leaders will start examining the detailed costings. Nato's plan to send in 40,000 troops for just six weeks to withdraw the UN peace- keepers would have cost pounds 4.5 bn. The cost of this operation, involving many more troops and lasting a year, will drain military coffers throughout the world. Nato hopes that all UN countries will share the burden of sending the force.
Nato leaders at Williamsburg are also expected to produce a detailed plan of what tasks the troops will perform. Monitoring the ceasefire will be the first need, but the force will also be required to set up de-militarised zones and to carry out mine clearance, as well as preventing renewed outbreaks of fighting.