German opposition leader Angela Merkel called on Thursday for the ratification process of the EU constitution to continue despite the rejection of the treaty by France and the Netherlands.

Merkel, the Christian Democratic Union (CDU) leader, echoed the reaction of German Chancellor Gerhard Schroeder, who she will challenge in a general election expected to take place in September.

"We must continue the ratification process," Merkel said, but she added it was essential to "take into consideration people's concerns".

However, Merkel repeated her call for the "excessive bureaucracy" related to the European Union to be reduced.

Schroeder said on Wednesday that he "respected but greatly regretted" the decision of voters in the Netherlands, who like Germany were a founder member of the European Union.

But he defended the treaty which Germany's two houses of parliament ratified with overwhelming majorities although it was not put to a referendum.

"I am convinced that we need the constitution if we want a democratic, social-minded and strong Europe," Schroeder said.

"The ratification process must continue. Firstly out of respect for the nine countries which have already ratified it, and secondly because of the member states who still have to undergo the ratification.

"Every member state has the right, and a duty, to go through its own vote."

Foreign Minister Joschka Fischer said the outcome was "regrettable and leaves Europe with a big challenge".

"It is not the end of the process of ratification and certainly not the end of European integration," he added.

The Baltic state of Latvia on Thursday became the tenth country to ratify the constitution.