Poland, Italy, Austria and Bulgaria are topping the list of trouble-makers, with Warsaw seeking to formalise its voting compromise in the new treaty; Rome pressing for more seats in the European Parliament; Vienna concerned by an influx of foreign students; and Sofia unhappy with the spelling of the word 'euro.'

However, Portugal - currently chairing the EU - has indicated none of the pending issues is serious enough to block the union's overall agreement on a new set of institutional rules - known as the Reform Treaty.

"If the atmosphere that I have found here today, if the understanding and the willingness to progress remain the same...we can do it in a more or less rapid way", said Portuguese European affairs minister Manuel Lobo Antunes.

But he stopped short of revealing any details on a possible compromise for any of the open issues.

The longest dispute centres around a Polish demand to have a decision-blocking mechanism written into the treaty, something that would equip Warsaw with a strong legal tool in the decision-making process. Currently it is written in a declaration which has no legal standing.

The mechanism - known as the Ioannina clause - enables a small number of member states to delay a decision made by a majority of countries if the decision hurts the interests of a particular country.

Warsaw 'constructive'

Other member states fear, however, that if the clause is written into the treaty then its use will become the rule rather than the exception.

But Mr Antunes on Monday (15 October) praised Warsaw for its "constructive and positive" attitude, saying he saw "a very strong will to come to an agreement in Lisbon". "It was something that had encouraged us", he added.

Meanwhile, Italy has become another hard nut to crack at the EU summit.

The Italian government is demanding that a decision on how seats in the EU Parliament should be distributed within the 27-nation bloc is postponed.

The agreement is something that should normally become a part of the EU's new treaty and enter into force with the next parliamentary elections in 2009.

But Rome - which under new rules would get the right to 72 deputies, six less than at the moment - insists there is no binding legal link between the go-ahead for the treaty and the composition of the parliament, agreed by MEPs themselves last week.

Portugal, for its part, has issued only a vague message on the issue, with Mr Antunes saying "the Portuguese presidency, when it has a task, likes to fully complete that task".

Austrian universities

On the other hand, better prospects are emerging in the case of Austria and Bulgaria.

Vienna recently raised the issue of foreign student access to its universities in the face of the great amount of German students enrolling in its medical schools.

"We encourage the European Commission and Austria to find a solution to this problem", Mr Antunes said, underlining there is a great deal of understanding of the Austrian problem within the EU bloc.

Similarly, Sofia is expected to get its way regarding the Bulgarian spelling of the euro - evro.

"We believe those are the citizens' aspirations. The solution that we will try to find for Bulgaria will have this perspective", Mr Antunes said.