By Jonathan Marcus
BBC diplomatic correspondent
George W Bush did not get it all his own way at his last Nato summit
This is turning out to be a distinctive Nato summit in a number of ways.
It will be US President George W Bush's last before he leaves office.
It will be the first, and last, at least as Russian president, for Vladimir Putin - he will be here on Friday.
It is also unusual in that these events are carefully prepared and usually highly scripted.
But this time key decisions on Nato enlargement went down to the wire, only being resolved at the opening dinner of the alliance heads of state and government.
President Bush came to Bucharest with an ambitious agenda, confident that he would get what he wanted.
In practice it has been a mixed outcome.
On Nato enlargement the US leader wanted an expansive package deal involving invitations to three new members - Albania, Croatia and Macedonia.
He had also sought an "intensified dialogue" with Bosnia-Hercegovina and Montenegro.
And he had called for membership action plans for Ukraine and Georgia.
In the arcane world of Nato terminology these categories of co-operation have clear meanings and send clear signals.
It is obvious what membership means.
A membership action plan is a kind of waiting room for prospective members involving a whole range of political and diplomatic contacts with Nato.
An intensified dialogue is a step below this.
Nato leaders were willing to extend invitations of membership to Albania and Croatia, but not to Macedonia, or at least not until it resolves its row with Greece over its name.
This is probably one of the more bizarre contemporary diplomatic disagreements, but the Greeks fear that Macedonia retains claims to Greek territory. The Macedonians say they do not.
President Bush could not convince all of his partners to back membership action plans for Ukraine and Georgia.
Germany in particular was uneasy.
And the US seems to have misread the diplomatic mood within the alliance, finding that there was far more support for Germany, and indeed Greece, around the dinner table than they had expected.
It was not a total rebuff, since the Nato communique virtually promises these two countries Nato membership at some time in the future.
That in itself may be enough to upset the Russians.
And Ukraine's and Georgia's status will be reviewed by Nato foreign ministers when they meet in December.
Indeed there was more bad news for Moscow on the missile defence front.
President Bush wanted to get Nato's backing for US plans to deploy a limited anti-missile defence system in Poland and the Czech Republic.
Incoming Russian President Dmitry Medvedev is against enlargement
He won the strong endorsement of his allies, ending more than a year of hesitation and uncertainty.
The Nato leaders agreed there is indeed a missile threat from the Middle East (for that read Iran).
They accepted that the US system does indeed contribute to allied security.
And they said steps had to be taken to deploy a parallel Nato system to defend any countries not covered by the US scheme.
Nato military planners were ordered to study how such a system might work and report back to the next alliance summit in 2009.
Consensus on missile defence is a significant achievement for President Bush, who wanted to get full Nato support for the project before he leaves office.
The alliance had been deeply divided on the whole issue.
So what has changed over the past year or so?
First of all Nato's own studies have convinced the allies there is indeed a potential missile threat.
France and Germany were against admitting Ukraine and Georgia
Secondly the US has re-packaged its proposals in a more Nato-friendly way.
But above all Nato countries are now convinced that US efforts to co-ordinate their plans with Russia are serious.
The ball now is thus very much in Moscow's court.
There was progress too on Afghanistan.
France agreed to send in extra troops, which will allow the US to re-distribute its forces, thus removing Canada's threat of withdrawal.
There was also a significant effort launched at this summit to try to get the military and civilian aspects of nation-building in the country working more harmoniously.
So far then a mixed picture for the Americans: success on the missile defence front, more nuanced progress on enlargement.
It is not so much that anyone is against enlargement in itself.
But there is a certain unease in some countries about upsetting the Russians.
In others there is a growing question about just how far east Nato enlargement should go.
Hundreds more French troops will go to Afghanistan
There used to be a defence magazine called Nato's Sixteen Nations.
In the end they had to give up the number in their title as the alliance expanded.
Now such a magazine would have to be called "Nato's Twenty-Six Nations and Counting"!
Nobody knows quite where this process might end.
Maybe that is why the alliance's Secretary General, Jaap de Hoop Scheffer, indicated there would be a full-scale study of Nato's future role ahead of the 2009 summit.
Nato is not closing its doors, but there are new actors on the stage.
The European Union aspires to a greater security role, now apparently with Washington's blessing after a fast-developing Franco-US entente.
Old players like Russia are back - they may not be granted a veto, but they also cannot be ignored.