Europe must cooperate more closely if it wants the euro to succeed as its shared currency, and it still has a long way to go to overcome its sovereign-debt crisis, German Chancellor Angela Merkel said in her New Year's Eve address.

Merkel said she would do everything in her power to strengthen the euro, but that this would only work if Europe learned from its mistakes.

A common currency can only really be successful if we in Europe cooperate more than we have done, Merkel said in a prerecorded televised address to be broadcast on Saturday.

Europe is growing together in the crisis, she said, according to an official copy of her speech.

The path to overcoming this remains long and won't be free from setbacks, but at the end of it, Europe will emerge stronger from the crisis than it went into it.

Merkel also said that while the German economy was doing well, next year would without a doubt be more difficult than this one.

Germany recovered swiftly from the 2008-2009 financial crisis, but growth has eased in the last few months, and many economists are now forecasting a mild slump for Europe's bulwark economy.

(Reporting by Sarah Marsh; Editing by Hugh Lawson)