Consumer confidence in Germany is being dampened slightly by the enduring wrangle over Greece's debt crisis, a poll has found.

"The hitherto marked optimism among consumers has received a slight knock," market research company GfK said in a statement. 

"Despite the deal reached with Greece over its debt, the downward trend in economic expectations has intensified with the third consecutive monthly decline," the statement said. 

That, in turn, has weighed on consumers' willingness to spend money and on their income expectations, GfK continued. 

Another negative factor was a slight increase in households' willingness to save, it added. 

Looking ahead to next month, GfK's headline household confidence index was forecast to slip to 9.9 points in September from 10.1 points in August. 

"Despite the decline, however, it cannot be said that Germany's economic motor, consumption, has stalled or even choked off," GfK said. 

The indicator remains at a high level, "which suggests that private consumption will continue to live up to its role as one of the main pillars of the economy this year," it said. 

"As it can be assumed that the conditions for domestic demand -- including employment, income and inflation -- will remain positive in the coming months, there are good chances that the consumer climate will stabilise again," GfK said. 

The unstable international situation, particularly in the Middle East, represented the main risk for the German economy it added.