By David Loyn
Developing World Correspondent, BBC News
Nato officials will be engaged in intensive discussions during the next few weeks following a formal invitation from the African Union (AU) for military help in the Darfur region of Sudan.
More than two million Darfur residents have fled their homes
The AU is significantly scaling up its forces, from 2,200 to more than 7,700 - made up of 5,500 soldiers, 1,600 civilian police officers and 700 military observers.
But spread across the huge region of Darfur, which is the size of France, even this larger force will have little effect against the light, mobile guerrilla forces of the Janjaweed.
The militias have continued to harass the civilian population, burning people out of their homes, in defiance of international protests.
In order to give them the flexibility they need, the AU wants Nato countries to provide logistical support, including communications, and the heavy-lifting capacity which no African armies have at their disposal.
Nato officials stress that there is no request for Nato combat forces - all of the contingency planning now is for this logistical back-up for the expanded AU force, crucial to enable it to be to able move large numbers of troops over long distances.
Chief Nato spokesman James Appathurai said planning was now going on to find out "what is already on the ground, and what now needs to be done".
Nato is the only credible international alliance which is able to undertake this.
Nato is the world's most powerful regional defence alliance
The EU has been trying to agree on plans for so-called 'battle groups' designed to be deployed at short notice for famine relief or conflict prevention in Africa.
But that capability is some years away from being operational.
The UN, which is currently putting together a peacekeeping force to monitor the ceasefire in southern Sudan, does not have any military capability of its own.
In particular it does not have the large planning department which Nato has kept - a legacy from the days of the Cold War when Western Europe was on constant alert against the threat of a Russian invasion.
Preliminary assessments will be made in time for a visit by an AU delegation to Nato headquarters in Belgium on 17 May.
Planners are aware of the need for speed.
Even at the best of times, it is hard to ensure effective regular supplies of aid.
When the rains come in June and July, and again in September, the dirt tracks become impassable quagmires.
It is then that Nato air transport could really make a difference.
But there is significant caution ahead of this first deployment of Nato forces into Africa.
Darfur has exposed the AU's weaknesses
Individual countries have, of course, sent forces before.
The US, France and Britain are the most prominent of those who have recently sent forces into Africa, and these three countries would be likely to form a significant role in the humanitarian mission to Darfur.
France, the most heavily-committed Nato country in the region already, with forces in neighbouring Chad, is the most cautious about formal Nato involvement.
Aware of these sensitivities, the official Nato statement announcing the move said "these consultations should go forward in a pragmatic way".
Nato is not rushing into Darfur.
The Sudan crisis is the first real test of Africa's will to sort out its own problems through the AU, but the continued high death-toll in Darfur has exposed the frailty of the organisation.
Even where there is political resolve, the continent does not have the capacity on its own to make a meaningful difference.
Now, with continued international concern over the region, the will to help from outside is increasing.
US military logistical assets are bound to form a component in any Nato operation, so that it can fulfil its obligations eight months after declaring that what is happening in Darfur amounts to genocide.
The UN Security Council has recently adopted two resolutions on Darfur, one imposing sanctions and the other making it possible to refer the matter to the International Criminal Court.
But there is some evidence to show that without action to back up words, these resolutions actually make things worse.
Foreign aid workers on the ground report that Sudanese officials sometimes withdraw co-operation and block their work, blaming them for the UN resolutions, and claiming that they must have given "wrong information" to their home countries.