"Reports that Germany is pursuing plans for a smaller eurozone are false," government spokesman Steffen Seibert said in a statement on microblogging website Twitter.

"The German government, on the contrary, wants to stabilise the eurozone as a whole."

A French source also dismissed the reports out of hand, saying there were no plans to shrink the ranks of the 17-member eurozone.

In light of speculation about a potential breakup of the currency union, European Commission chief Jose Manuel Barroso said in Berlin late on Wednesday: "The EU as a whole and the euro area belong together and should not be divided."

French President Nicolas Sarkozy had spoken on Tuesday of a future "two-speed Europe" anchored in a "federal" eurozone, sparking concern of political exclusion among EU members not using the common currency.

British Deputy Prime Minister Nick Clegg said on Wednesday that the calls to change the EU treaty and reorder the bloc's makeup were "melodramatic", while in Brussels for talks with EU president Herman Van Rompuy ahead of a summit next month looking at a German-led bid to rewrite the EU's rulebook.

And German Foreign Minister Guido Westerwelle said on Wednesday that EU countries should be able to opt whether to take part in European treaty changes on fiscal reform in light of reluctance among some non-eurozone members.

German Chancellor Angela Merkel had said earlier in the day that the EU was "not viable" without treaty changes that would place stricter controls on public finances, allowing the bloc to become a "stability union."