The decision will raise the hopes of prospective central and east European members, though they have pressed for a more binding guarantee, with a timetable and criteria for membership.
The move will be seen as a vital step towards filling a security vacuum in countries once occupied by Soviet troops.
Several points remain unresolved on the eve of President Bill Clinton's arrival in Brussels, but all the indications are that deadlock on enlargement has been broken, leaving a compromise that is more far- reaching than some Nato members wanted but less radical than East Europe hoped.
According to the draft declaration, alliance leaders will say they have 'agreed that we would expect and welcome Nato expansion that would reach to democratic states to our east, as part of an evolutionary process'. Speaking in Brussels yesterday, Manfred Worner, Nato's secretary-general, said: 'This can be done in a carefully measured evolution over time.'
Membership will evolve out of Partnership for Peace, the US initiative for pacts between Nato and central and eastern European countries. Those will lead to joint exercises next year, give states the right to Nato security consultations, and help to bridge gaps between different countries' military equipment. Each state will propose a work plan.
Yesterday, the defence chiefs of Hungary, Poland, the Czech Republic and Slovakia welcomed the initiative, calling it 'a step in the right direction', but they wanted firmer guarantees that it would lead to membership. They were due to be briefed by Madeleine Albright, US ambassador to the United Nations, and General John Shalikashvili, the US armed forces chief. A senior alliance source said consideration was being given to a review of the partnership agreements to create a half-way house of associate membership or put some states into a 'fast track' for membership.
The summit may propose a link between membership of Nato and the European Union.
It is unclear how Russia, which has opposed expansion, will react. The draft declaration contains a passage praising its efforts for political and economic reform, including the recent parliamentary elections which brought to prominence Vladimir Zhirinovsky, the ultra-nationalist. The document indicates the summit may attack Ukraine's failure to respect nuclear disarmament treaties.
An East Europe deal is a necessary condition of unity for a summit intended to cement the transatlantic alliance. The US, France and Britain have resisted faster progress on enlargement, advocated by Germany, fearing it would antagonise Russia and weaken the alliance.Reuse content