With opinion polls showing the "no" camp in front days before the vote, the two left-wing European leaders targeted generally pro-European Socialist Party (PS) supporters in France, seen as the key to the outcome.
Schröder on the stump in France
German Chancellor Gerhard Schröder and Spanish Prime Minister Jose Luis Rodriguez Zapatero joined the last day of campaigning for the French referendum on the EU constitution Friday in a bid to convince skeptical swing voters to approve the treaty.
"Spain votes 'yes', France votes 'yes' and Europe votes 'yes'," Zapatero told a rally hosted by Socialist party leader Francois Hollande that was attended by about 3,000 people in the northern city of Lille.
"Europe needs France, its enthusiasm, its culture, its strength and its momentum," he said, adding that Europe would not make progress without France. "The 'no' is sad and pessimistic," he added. "We want Europe because it means peace, freedom and solidarity."
Spanish Prime Minister Jose Luis Rodriguez Zapatero holds his ballot in a polling station in Las Rozas on the outskirts of Madrid, Sunday, Feb. 20, 2005 as Spaniards started voting on it in the referendum to ratify the EU constitution.
Zapatero was returning a favor to French President Jacques Chirac, who visited Barcelona in February to back the "yes" camp ahead of the Spanish referendum.
European Union leaders are increasingly worried that a rejection of the treaty in Sunday's referendum in France will deal a bitter blow to the bloc's first constitution, aimed at simplifying EU operating rules.
After Germany became the ninth country to ratify the EU charter on Friday, Schröder addressed a rally of between 700 and 800 people for the "yes" campaign in the southwestern city of Toulouse alongside former French minister Dominique Strauss-Kahn.
Schröder asked the French to "vote 'yes' with all their heart and their head." France and Germany have a great responsibility for Europe to last eternally and must assume that responsibility for future generations, Schröder said.
Spain was the first country to hold a referendum on the EU constitution on February 20 and those voting backed it overwhelmingly, a sharp contrast to a more skeptical France.
Left is divided
France's opposition Socialists are deeply split on the EU constitution, with the party leadership backing the text and dissidents led by former Prime Minister Laurent Fabius opposing it.
Valery Giscard d'Estaing
Former French president Valery Giscard d'Estaing, who oversaw the process of drawing up the constitution, defended the treaty in an address to Germany's upper house earlier in the day. He called on France not to derail the European project by voting "no".
"The day after tomorrow, I hope with all my heart that the French are going to ratify this constitution through a referendum," Giscard d'Estaing said. "Ratification by Germany and France would mark an historic step forward for the future of the constitution and for Europe."
By completing the ratification process, Germany followed in the footsteps of Austria, Greece, Hungary, Italy, Lithuania, Slovakia, Slovenia and Spain.
All 25 EU member states must approve the constitutional text before it can take effect. Rejection by France, one of the bloc's six founding members, would likely plunge the European Union into political uncertainty.
In wake of domestic defeat
Schröder's visit to France came at a difficult time for him politically, after he called for an early general election following a key state election defeat for his Social Democrats, but German support for the constitution is strong.
Both Schröder and former chancellor Helmut Schmidt have made urgent appeals to the French to back the constitution, with Schröder warning France last week "not to leave the other Europeans in the lurch".
"Europe is stronger when it speaks with one voice. We need a strong Europe, an integrated Europe," he said.
German Foreign Minister Joschka Fischer in France in April lending his support the French governement's campaign for the"Yes" to the constitution.
German Foreign Minister Joschka Fischer meanwhile has hailed the constitution as a "fantastic project" which would allow Europe to face up to an increasingly globalized world.
Earlier this week, Zapatero called on French voters to back the treaty, saying it would "facilitate construction of our social model, without doubt the best and fairest in the world."