Germany became the ninth country to ratify the EU constitution on Friday in a move designed to help the flagging "yes" campaign in France ahead of this weekend's referendum.

The upper house of parliament, the Bundesrat, voted overwhelmingly in favour of the treaty by 66 votes out of a possible 69 with three abstentions.

Germany followed Austria, Greece, Hungary, Italy, Lithuania, Slovakia, Slovenia and Spain in approving the text which is designed to set out a new framework for an enlarged European Union.

All 25 EU member states must approve the constitution before it can take effect.

German political leaders have expressed grave concerns about the consequences of a "no" vote in France, the other half of the so-called German-French "motor" of European integration.

Foreign Minister and Vice-Chancellor Joschka Fischer told the upper house that if the constitution was rejected it would make the continent "weaker" and hinder its ability to compete in an increasingly globalised world.

"The world will not wait for Europe," Fischer said.

He dismissed concerns about the constitution leading to an influx of low-cost labour from eastern Europe, saying people forgot that 20 years ago western Europe saw an influx of workers from Portugal, Greece and Spain. Those countries were former dictatorships which had now become prosperous democracies, Fischer said.

Germany did not put the constitutional charter to a popular vote.

The lower house of parliament, the Bundestag, had approved it with a massive majority on May 12.

Former French president Valery Giscard d'Estaing, who helped draft the constitution, made an address to the German upper house in which he called on France not to derail the European project.

"This is an historic event because Germany is one of Europe's founding countries and its most populous," Giscard d'Estaing said.

"The day after tomorrow, I hope with all my heart that the French are going to ratify this constitution through a referendum.

"Ratification by Germany and France would mark an historic step forward for the future of the constitution and for Europe."

In another sign of Germany's concern over the French referendum, Chancellor Gerhard Schroeder was breaking off from planning a general election expected in September in order to visit France on Friday to urge voters to back the text.

He was to address a French Socialist Party rally in the southwestern city of Toulouse.

Schroeder warned France last week that it had a responsibility "not to leave the other Europeans in the lurch".

Opinion polls in France showed the "no" camp had a clear lead with 48 hours to go before voting.

Le Parisien newspaper said 55 percent opposed the text with 45 percent backing it.

Backers of the constitution say the EU needs new structures to cope with the admission last year of 10 new members, eight of them former Communist countries.