"This is not just up to us, but we will do our part. If that doesn't succeed, it will not be the downfall of Europe, but it will have extremely serious consequences for the future of Europe," Merkel said.

She stressed that there was still a lot to do to move forward the debate on the draft constitution, which was rejected by French and Dutch voters in referendums in 2005.

Merkel also cautioned that a solution to the dispute with Poland was not yet in sight in her speech to the German parliament on Thursday, a week ahead of the EU summit in Brussels.

But shortly afterwards, Polish President Lech Kaczynski signalled that Poland would seek a compromise over its opposition to the proposed voting system. Kaczynski said he wanted to avoid the isolation of his country over the issue.

Glimmer of hope?

Warsaw had threatened to veto a deal on the future of the charter because of the planned changes, which Poland says favor the bloc's bigger states.

Germany is currently the holder of the rotating presidency, but its tenure ends at the end of June. Merkel had declared it her goal to break the deadlock over the EU treaty.

The chancellor reiterated her position that the draft constitution would not be completely abandoned when any new treaty is drawn up.

"We want to keep the substance of the treaty without over-burdening people," she told lawmakers. "Any solution we do find must be in a form that helps Europe."

The chancellor said it was essential to find a solution to the treaty issue so that a bloc that has enlarged into eastern and southern Europe is "able to function properly." The EU has expanded from a 15 to a 27-member bloc over the last three years, making reform necessary.

Challenging times

"Europe faces great challenges both within, and more importantly, outside its borders," she said.

In addition, Merkel stressed that it was necessary for a new constitution to better meet the wishes of European citizens. This would involve making clearer the division of power between the bloc and its member states.

Fears about the creation of a European super-state must also be taken into account, Merkel told legislators.

The chancellor gave a more positive evaluation of what had been achieved at the G8 summit, in particular over climate change, during her Bundestag speech.

She said that without the EU's agreement on binding emission reduction goals the agreements reached at Heiligendamm would have been "completely inconceivable."