EU leaders have set 2008 as a target for making changes to the EU rule book, which are needed for further expansion.
The leaders said there were no new criteria for further enlargement
A constitution setting out a series of such reforms was rejected by France and Holland last year, and the EU is split over whether it can be revived.
Germany will suggest ways of continuing the reform process next year, with the "necessary steps" being taken in 2008.
The leaders also proposed a list of practical policies designed to show the EU makes a difference to voters' lives.
In other decisions, the 25 leaders:
- agreed to televise meetings of EU ministers
- said they would honour commitments made to countries that want to join the EU
- asked the European Commission to draw up a report on the EU's ability to absorb new members
- urged Bulgaria and Romania to carry out crucial reforms that will enable them to join the EU on time in January
- said Slovenia can introduce the euro in January
- backed a plan for donors to release emergency aid to the Palestinians, bypassing the Hamas-led government
On the question of enlargement, the summit debated how much weight to give to the EU's capacity to "absorb" new members, amid signs that public opinion in some Western European countries is cool towards further expansion.
Austrian Chancellor Wolfgang Schuessel said the leaders had dropped the idea of making "absorption capacity" an additional criterion for further enlargement.
The leaders asked the European Commission to produce a report this year to define exactly what absorption capacity is.
The President of the European Commission, Jose Manuel Barroso, told the BBC on Thursday that all democracies had to take account of public opinion.
He added that it was possible for Turkey to join the EU, but it would be very difficult.
"First of all (it will be) very demanding for them but also demanding for us here to be ready to accommodate such an important big country that is seen by so many of us as culturally different from, let's say, mainstream Europe," he said.
On the constitution, EU members are split between those who would like to bury it and those who would like to revive it, in one form or another.
Some countries, including the UK and Poland, opposed the idea of setting a timetable for institutional reforms.
But UK Prime Minister Tony Blair said there was an obvious need to look at how Europe can operate more effectively when it is expanding "so greatly".
He said the timetable for expansion gave the EU "effectively another couple of years" to do this.
The leaders' decision to approve a list of practical policies, aimed at regaining voters' trust after the failure of the constitution, stems partly from a UK initiative launched at a summit in Hampton Court last year.
"I think what citizens want out of Europe is to concentrate on the bread and butter key issues - about the economy, about illegal immigration, about security - that really worry them," Mr Blair said.
If the EU was seen to be delivering real change for the better, he added, voters would be more likely to say Yes when asked to approve to institutional reforms.