* UBS may pass on negative rates to more clients -CEO
* Has already upped fees for corporates, institutions
* CEO Ermotti says saw low transaction volumes in Q3 (Recasts with CEO comments on negative rates, adds shares)
By Joshua Franklin
ZURICH, Sept 29 (Reuters) - UBS, the world's biggest wealth manager, could pass on negative interest rates to more depositors if Switzerland's central bank persists with sub-zero rates, Chief Executive Sergio Ermotti said on Thursday.
Interest rates in UBS's native Switzerland have been set at -0.75 percent since January 2015. The policy has undermined UBS's ability to protect net interest income -- the spread between what banks earn from lending and what they pay on their liabilities -- Ermotti said.
UBS has already upped fees for corporate and institutional clients as well as raising mortgage rates by 50 basis points and accepting a smaller share of the market, but Ermotti cautioned this might not be enough if negative rates persisted.
"We may need to start to think about how to pass more negative rates to a broader client base than being able to reprice the asset side of the equation," Ermotti said at a Bank of America Merrill Lynch conference in London.
UBS holds around 400 billion Swiss francs ($412 billion) in cash deposits with roughly half in its wealth management business, he said.
The SNB is using negative deposit rates in an effort to weaken the Swiss franc and protect Switzerland's exporters.
Ermotti also struck a cautious tone in his outlook for third-quarter results, echoing the CEO of rival Credit Suisse , Tidjane Thiam, earlier this week.
"With respect to what we have experienced so far in the third quarter, normal seasonality, underlying macroeconomic uncertainty and heightened geopolitical tensions continue to contribute to client risk aversion and generally low transaction volumes," Ermotti said.
"In some businesses and regions in which our IB (investment bank) operates, conditions have remained challenging through the third quarter," he added.
Shares in UBS were down 0.2 percent at 0945 GMT, lagging the European banking sector index which was up 0.6 percent.
UBS reports third-quarter results on Oct. 28.
$1 = 0.9708 Swiss francs Editing by Michael Shields and Alexander Smith