Germany and France, the European Union's dominant powers, want to amend the EU's main law, the Lisbontreaty, to create a permanent system for handling financial crises such as Greece's debt collapse.
There was initially strong opposition to the proposal from most other countries in the bloc, but there are signs that support for the idea is growing, even if concerns remain about how such changes would be carried out.
Altering the treaty, which took eight years to negotiate and came into force only last December, is no straightforward task. It would have to be agreed unanimously and ratified by all 27 EU countries and the European Parliament, a process that could prove politically divisive and take a long time.
There are a variety of ways in which treaty change could be enacted, depending on how far-reaching the proposals are and the legal preparation for such a move. EU leaders are discussing the issue at a summit inBrussels on Thursday and Friday.
Following is a look at some of the scenarios.
Substantial treaty change
One risk of amending the treaty is that once it is open for discussion, every EU member state and the European Parliament may step forward with its own proposals. The treaty could unravel as a range of clauses are picked apart and reassessed. If Germany is intent on securing the changes it wants, it may have to agree to tweaks that Britain, the Czech Republic, Italy or Greece, for example, want as part of the grand bargaining that often underpins the EU legislative process.
The more amendments proposed, the harder it will be to secure unanimity, the longer the task will take and the greater the risk that it is not completed by 2013, when the temporary crisis mechanism expires, raising market uncertainty.
It also means it would be tougher to secure each member state's backing, putting the ratification process at risk. Countries like Ireland, Denmark, Sweden or the Netherlands would have to hold a referendum on the adjustments, a high barrier and one that Ireland, in particular, will not want to repeat after it rejected the Lisbontreaty in a referendum in 2008.
Britain would also oppose a big revision of the treaty as it could mean the transfer of more power fromWestminster to Brussels, which the government has said it will not allow.
Seen from the outside, the EU would look weak and indecisive if it started making major adjustments to its fundamental treaty barely a year after the charter was finally approved after nearly a decade of negotiation.
All member states appear intent on avoiding a wide-ranging alteration of the treaty.
Narrowly defined changes
A preferred option is to strictly define the proposed changes before the process begins so that it effectively becomes key-hole surgery on the Lisbon treaty, not a free-for-all.
Such a scenario may involve opening up only one or two clauses in the treaty to insert the necessary language on a permanent crisis mechanism and ensure it is consistent with the "no bailout" clause that already exists in the treaty.
Small adjustments could also include language making clear the changes are focused only on the 16 countries in the euro zone, not the whole EU, which might satisfy Britain that there is no transfer of power.
Depending on how tightly defined the changes are, it might also mean countries such as Ireland would not have to hold a referendum on the issue, smoothing the ratification process.
One sticking point will be the European Parliament. Under the Lisbon treaty, parliament's powers of oversight and legislative consultation have been greatly enhanced. Parliament would have to be part of any intethe forum in which EU treaty changes are negotiated and would be likely to have strong views on the process.
If the proposed treaty changes are limited, Germany and France might be able to persuade parliament to forego an intergovernmental conference, streamlining the treaty revision process. But parliament will expect something in return.
No treaty change
Germany is adamant about the need to change the treaty, saying there is no other way to create a legally sound permanent crisis mechanism that satisfies its constitutional court.
But the European Commission, the EU's executive, believes it may be possible under the Lisbon treaty to establish such a mechanism without changing the treaty, and Finland has put forward concrete proposals that would not need a change in the charter.
An annex could be added to the treaty that would be approved by all EU member states at the same time thatCroatia signs an accession treaty in mid-2011.
EU sources say lawyers are already working to establish the legal and constitutional groundwork for such possibilities.
The benefit is that it could probably be carried out much more quickly than a proper treaty change and with much less political disruption in those EU member states whose people, governments and parliaments are sceptical about changing the Lisbon treaty.
But it may not satisfy Germany, which worries that anything short of treaty change could be successfully challenged in its constitutional court. It may also lead to broader legal battles.
For example, Germany wants the treaty amendment to include a stipulation that the private sector bears more of the risk under the permanent crisis system. That could be challenged in court if the alterations were made without treaty change.
