German Minister for Economic Affairs Sigmar Gabriel appealed on Wednesday to the nation's top court to reject a last-ditch attempt to stop an European Union-Canada trade agreement from coming into force.
If the signing of the Comprehensive Economic and Trade Agreement (CETA) failed to go ahead this month, it would throw the whole future of the deal into doubt, said Gabriel, who is also vice-chancellor.
"I do not want to imagine what that could mean for Europe," he told the Constitutional Court in the western German city of Karlsruhe. He argued that no-one around the world would have confidence in the capacity of both Germany and the EU to sign contracts.
Opponents of the agreement between the EU and the world's 10th biggest economy want the court to issue a ruling forcing the German government to vote against CETA.
In his opening remarks, the court president Andreas Vosskuhle said both "proponents and opponents of the agreement often tended to simplify ... a very complex agreement".
Vosskuhle said the court had "to take sufficient account of the complexity of the subject matter" in making an assessment of the agreement, which took about seven years to negotiate.
EU trade ministers are to set out their government's stance on the deal at a meeting next Tuesday.
This would then pave the way for a summit of European and Canadian leaders set down for October 27, which has been called to formally sign off on the accord.
The summit would then launch the ratification process with all of the EU's national parliaments as well as the Canadian parliament having to agree to the accord.
However, CETA critics fear that the agreement could provisionally come into force in the EU before the approval of national parliaments, with the European Parliament likely to consider the deal at the start of next year.
The panel of judges led by Vosskuhle are due to announce a verdict on Thursday.
EU and Canadian leaders argue that by abolishing tariffs and non-tariff trade barriers, the agreement will help to stimulate economic growth and create jobs.
But CETA opponents, which include the hard-left Die Linke party and the consumer organization Foodwatch, claim the trade deal will lower the EU's consumer and environmental standards and that the negotiations were held behind closed doors.
"Parliaments are no longer to play a role in shaping (the agreement), they can only say yes in the end," said Roman Huber from the citizens action group More Democracy, which is representing a record of more than 125,000 co-plaintiffs in the case.
However, Gabriel hit back telling the court the EU was attempting to introduce rules that safeguard European standards.
Earlier on Wednesday, anti-CETA activists handed over to German Chancellor Angela Merkel's office in Berlin a petition signed by 337,000 people opposing the agreement.
The EU is Canada's second most important trading partner after the United States.
Consequently, CETA is also considered by officials as helping set the stage for plans for a more controversial trade deal between the EU and the US, which is facing even stiffer opposition on both sides of the Atlantic.