BERLIN (Reuters) - Germany and France have begun working on a joint package to stem the euro zone debt crisis, but it will not be a "miracle cure" for the bloc's ills, Chancellor Angela Merkel's spokesman said on Monday.

Merkel hosted French President Nicolas Sarkozy for talks on Sunday evening, and at a joint presser, they promised to unveil a comprehensive new package for the euro zone by the end of October. Both leaders refused to provide details on what the package would contain.

"The German and French governments are convinced this will be a contribution to the euro zone winning back confidence and its capacity to act -- and I do mean a contribution, not the 'miracle cure' everyone keeps asking for," said Merkel's spokesman Steffen Seibert.

The leaders signaled the package would include an agreement on recapitalizing European banks, dealing with Greece's debt woes and on moving forward with closer economic coordination. Sarkozy vowed to produce it in time for a G20 summit in Cannes on November 3-4 that he will host.

Hopes for the Franco-German plan helped boost the euro and European shares on Monday.

Seibert told a news conference that the intention of Berlin and Paris was to release no further details for now, as the two governments had decided to work on the technical details "in confidence and confidentiality."

Asked if that meant only Germany and France were involved in thrashing out the proposals, Seibert said he believed both Merkel and the French president were in "constant contact with other European partners."

"But this work plan will be driven by German and France, of course always in agreement with European partners, but driven by these two countries," Seibert said.

Responding to a question about whether Greece in particular would be consulted in the details of the plan, Seibert said it would involve "measures for the euro zone as a whole and the stability of our currency overall, not measures for one single country."

(Reporting by Stephen Brown and Sarah Marsh; Editing by Noah Barkin)