BERLIN (Reuters) - The European Union's inability to complete a trade agreement with Canada is an embarrassment and could harm its ability to negotiate future deals, a European Parliament vice president said in a radio interview.

The Comprehensive Economic and Trade Agreement (CETA) has been seven years in the making and is backed by all 27 other EU governments but was rejected by the French-speaking south of Belgium, meaning Belgium as a whole cannot sign it.

"The European Union has shown itself to be an impossible international negotiating partner with this wrong whole process," Alexander Lambsdorff told broadcaster Deutschlandfunk.

The German Liberal lawmaker said he hoped Belgium could work out its issues over CETA to enable it to be signed this year.

Canadian Prime Minister Justin Trudeau canceled plans to travel to Brussels to sign CETA after Belgian politicians on Wednesday failed to break the deadlock over the deal.

Two other German representatives in the European Parliament also criticized the EU over the CETA negotiations.

Manfred Weber, head of a conservative bloc in parliament, told broadcaster Hessischer Rundfunk that it was a mistake to allow all European parliaments to vote on the trade pact.

"It cannot be that one small region can block all of Europe," he said.

Bernd Lange, a Social Democrat, told broadcaster Suedwestrundfunk that the stalemate on the agreement should prompt serious discussion about the European decision-making processes and how to create more consensus.

German Economy Minister Sigmar Gabriel said last week he did not expect CETA to fail, but it could take some time to answer questions raised by Belgium and other countries.

(Reporting by Gernot Heller; Writing by Andrea Shalal; Editing by Louise Ireland)