Anshu Jain, who along with Juergen Fitschen has run Germany's largest bank since 2012, said asking Berlin to spend more money to bolster the European economy was not the right approach, putting the onus squarely on other countries where the pace of reform has disappointed.

He did not name the laggards. But both France and Italy are under pressure to push through deeper reforms of their economies. French President Francois Hollande's government acknowledged last week that it would need until 2017 to meet European Union deficit targets, four years later than it initially pledged.

"My concern is that we may have squandered some of the time which was bought by the strong initial actions of national governments and the continuing interventions by the ECB (European Central Bank)," Jain told Reuters in Frankfurt.

"The pace and scope of reforms has not been strong enough to generate sufficient growth to address the sovereign debt overhang in some countries and, above all, to reduce unemployment, in particular youth unemployment."

Jain's comments come at a time when Germany faces pressure to step up public spending to bolster the 18-nation euro zone economy, which stagnated in the second quarter.

The International Monetary Fund (IMF), European Commission and ECB President Mario Draghi have all suggested that Berlin could do more to stimulate growth.

Some private economists also believe that Chancellor Angela Merkel's government should take advantage of its strong financial position to invest more in infrastructure and education.

But Jain said he was not convinced looser fiscal policy was the right way to get Europe growing again. Asking Germany to spend more, he said, was the "easy way out".

"Europe's problems are not insurmountable, but they require resolute actions on the part of national policy makers," Jain said, holding up the United Kingdom, Ireland, Portugal and Spain as countries that have made "impressive" progress on the reform front.

The German government has also pushed back against calls for higher spending, saying its own ambitious budget goals leave it little leeway.

In the coalition agreement sealed last year between Merkel's conservatives and the centre-left Social Democrats (SPD), the parties promised to achieve a structurally balanced federal budget in 2014 and, for the first time since 1969, refrain from new borrowing from 2015.

(Reporting by Noah Barkin, Thomas Atkins, Kathrin Jones and Alexander Smith, editing by John Stonestreet)

By Noah Barkin and Thomas Atkins