* Deutsche CEO says most won't benefit from lower rates
* Says low rates causing divisions, hurting banks
* Commerzbank CEO says ultra-low rates not sustainable (Updates with BlackRock CEO, additional Sewing quote)
FRANKFURT, Sept 4 (Reuters) - The CEOs of Germany's two largest listed banks on Wednesday warned that a further cut in interest rates by the European Central Bank would deal a blow to savers and the financial system while having only minimal effect on the economy.
The stern message comes a week before an ECB policy meeting at which decision makers are expected to lean towards a stimulus package that includes a rate cut.
Deutsche Bank CEO Christian Sewing told a banking conference that his company's customers had said they would not invest more if credit were 0.10 percentage points cheaper.
A rate cut would "only drive up asset prices and further burden savers", he said.
Lower rates would help those who are indebted or invested in assets, but the majority of the population would not benefit, he said.
"That divides society further," he said. Over the long term, low rates are ruining the financial system, he added.
Commerzbank CEO Martin Zielke backed Sewing's stance.
"I also don't consider this a sustainable, responsible policy," Zielke said.
Banks in Germany and across Europe have long complained about ECB policy which requires banks to pay to park their cash at the central bank, hurting their profits.
Banks in Germany paid 2.4 billion euros ($2.7 billion) to the central bank to hold cash in 2018, the German government said in response to a parliamentary inquiry on negative interest rates.
BlackRock's chairman and CEO said at the same conference that the people of Germany and France believe bank accounts, despite rock bottom interest rates, are the best place to keep their money.
"They are wrong," he said, pointing to stock markets and property as alternatives. "It is financial craziness," he added.
$1 = 0.8973 euros Reporting by Tom Sims, Patricia Uhlig and Hans Seidenstuecker; Editing by Jason Neely and Mark Potter