The German leader Angela Merkel says a new European Union treaty is needed in order to set up a fiscal union aimed at resolving the eurozone's chronic debt crisis.
Mrs Merkel told the Bundestag, the German parliament, that such a union would impose budget discipline. But she warned it will take years to resolve the crisis.
On Monday she is to meet the French president, Nicolas Sarkozy, who has also called for EU treaty changes.
Britain's prime minister, David Cameron, held talks with Mr Sarkozy in Paris on Friday and afterwards spoke against the French and German push for changes to the treaty.
The BBC reports he said steps could be taken to shore up the euro and improve the competitiveness of its weaker economies without treaty change.
Concrete steps promised
EU leaders have been under pressure to do more to tackle the debt crisis, amid concern about the survival of the euro.
In her speech, Mrs Merkel promised "concrete steps towards a fiscal union" - in effect close integration of the tax-and-spend polices of individual eurozone countries, with Brussels imposing penalties on members that break the rules.
"We need budget discipline and an effective crisis management mechanism," she said. "So we need to change the treaties or create new treaties."