by Paul Reynolds BBC News Online world affairs correspondent

The convoluted negotiations towards a constitution for the European Union which are supposed to reach completion in Brussels this weekend have muddied the European playing field.

EU leaders are supposed to reach agreement this weekend

There are some new boys in this game and they are giving the older ones the run-around.

France and Germany are suddenly having to watch their backs.

They have even invited Tony Blair to a pre-summit meeting as they seek to extend their alliances in this variation of the "old versus new Europe" row which marked the crisis over Iraq.

"Give us normality" was the plea of Central and East Europeans during their anti-communist revolutions.

They are now experiencing normality. It is called membership of the European Union and it means having to fight for your interests just as hard, even if in different ways.

Poles 'sold out'

Take the Poles. For centuries, they were battered and bashed.

Now, on the eve of EU membership next spring, they reckon they have been sold out.

The Poles are upset because they have been offered a less good deal than the one they already have.

But they have a trump card. If there is no new agreement, the old one will apply. The Poles are naturally playing that card.

In the previous treaty agreed in Nice in 2000, it was laid down that, in an enlarged EU, Poland and Spain would get a hefty 27 votes each in the system of weighted or qualified majority voting.

That was only two short of the 29 given to the big four - Germany, France, the UK and Italy.

This is a question on which we are not moveable Chancellor Schroeder

The Germans came off worst. Their population is about 80 million. The Poles and Spanish have about 40 million each. Yet Poland and Spain combined would have 54 votes against Germany's 29. But then, it was always a journalistic rule of thumb in Brussels that the Germans would give in. They did so in Nice.

The new constitution, however, is designed to overtake the Nice arrangements by simplifying the voting system. Instead of having to get 232 votes out of 321 to reach a majority, it is proposed that a measure be passed with a majority of countries representing 60% of the total EU population.

Fiasco on cards?

The Germans like the new plan and are not so willing to be imposed on any more. Chancellor Gerhard Schroeder has said: "This is a question on which we are not moveable."

But the Poles, aware that they can block the constitution and go back to the default setting called Nice, are equally adamant.

"We cannot, alas, rule out a fiasco because the extremely polarised positions are expressed in a radical way," said the Polish Foreign Minister Wlodzimierz Cimoszewicz.

The chances of reaching agreement in Brussels are 50-50 Heather Grabbe Centre for European Reform

He accused France and Germany of not respecting the rules of "fair play." Welcome to the EU, Warsaw.

It is possible that a compromise could be reached by allowing the Nice formula to work for a few years before the new system is brought in. The British, with their policy of fostering ties to "new Europe", have proposed a plan to look at this again in 2009.

It is charmingly described as a "rendezvous" clause. The rendezvous is likely to be a bruising one because Poland and Spain would exact a high price for change.

Farewell, solidarity

There is, however, a weakness in the Polish and Spanish position. It is their reliance on aid from other member states, especially Germany. This weakness will be exploited.

I have concentrated on this issue because it is one of the toughest facing the Brussels meeting. It shows how, when it comes down to the wire, high-minded European solidarity gives way to the cut and thrust of national interest.

Heather Grabbe of the Centre for European Reform in London said: "The chances of reaching agreement in Brussels are 50-50. Voting rights is the biggest problem. It has produced divisions. It pits the larger against the smaller states, Germany and France against Poland and Spain. "

But there are other issues as well. Britain has its red lines and will not permit majority voting in foreign policy or in anything to do with tax. There are arguments, too, about the size of the European Commission, the roles of a new EU foreign minister and the permanent President of the Council, and about defence.

The idea was to make the EU more simple not more complicated. Yet the changes are no easier for the public to understand Heather Grabbe, Centre for European Reform

Defence was at one time threatening to be a deal-breaker, but some sensible advance work has been done by Britain, France and Germany.

It is likely there will be a small EU planning unit for military operations which Nato does not want to conduct. Whether that turns into a threat to Nato remains for the future to decide. Governments don't look too far ahead.

Too complex?

According to critics like Heather Grabbe, the deals to settle the new constitution will make it too complex.

"The idea was to make the EU more simple, not more complicated. Yet the changes are no easier for the public to understand. It could be a great failure. The atmosphere is acrimonious. The Italian presidency has not done well. France and German threw their weight around over the stability pact and the small members feel bulldozed.

"There are fundamental divisions and there needs to be a package which buys everyone off - but that makes it even more complex."