"The supreme guarantee of the security of the allies is provided by the strategic nuclear forces of the alliance. New allies will share the benefits and responsibilities from this in the same way as other allies," the study says.
To ease Russian fears, Nato leaders stress that such deployment is unlikely. "There is no reason to contemplate any change in our nuclear doctrine or deployments," a senior Nato diplomat said yesterday.
On the stationing of forces, the diplomat was little more flexible, saying it was "conceivable" that alliance members might deploy troops within the new member countries, should a threat arise.
The study, which will be unveiled today, examines why and how Nato should expand to the east. But it avoids addressing the issue of which countries will join up first, and when.
The debate on enlargement is expected to last years. Nato sources yesterday warned that East Europeans qualifying to join the alliance may not be the same as those qualifying to join the European Union. However, interest shown in EU membership would influence Nato's decision on accepting new members in the military club.
The case for expansion has been made out only in general terms, to avoid stirring up Russian suspicions. On Tuesday General Alexander Lebed, a popular Russian nationalist, warned that the West risked provoking a third world war if Nato went ahead with expansion.
The timing of the Nato study may not help delicate negotiations over how Russian forces can be integrated into the Nato peace enforcement force to be sent to the former Yugoslavia in the event of peace. Nato enlargement has also stirred fears of a new arms race, as East Europeans are encouraged to make their forces compatible with Nato forces. The disarmament lobby, which criticises Nato for abandoning commitment to arms control, has predicted that the East Europeans will become customers of the US arms industry.
In return for joining the alliance, Nato's protective umbrella would be extended to the new members. They will have to be prepared to update their own forces and military infrastructure to be "compatible" with existing Nato forces, and in order to be able to deploy their forces in Nato operations.
The study stresses that enlargement should not undermine the efficiency of the alliance, saying that the issue of which countries join first will be based on their readiness to share the military responsibilities of the alliance.
"New members' forces would be expected to take part in the full spectrum of alliance missions," the study says.