NEW YORK (Reuters) -JPMorgan Chase ( JPM ) shares fell about 6% after the bank's president on Tuesday tempered expectations about its income from interest payments.

President and Chief Operating Officer Daniel Pinto said forecasts for net interest income (NII), or the difference between what the bank makes on loans and pays out on deposits, were overly optimistic.

"NII expectations are a bit too high," Pinto said, without providing a revised estimate. "Next year is going to be a bit more challenging."

JPMorgan ( JPM ) earlier forecast its NII would rise to $91 billion this year, excluding its markets division.

Meanwhile, investment banking fees could climb by 15% in the third quarter, Pinto said.

JPMorgan's ( JPM ) profit rose to a record in the second quarter, buoyed by a 46% jump in investment banking revenue. Rivals including Citigroup and Wells Fargo also reported strong gains in investment banking.

Revenue from JPMorgan's ( JPM ) newly-merged commercial and investment bank unit also jumped to a record $35.5 billion in the first half.

Trading revenue is expected to be flat or rise 2% in the third quarter, while volumes for mergers and acquisitions will probably stay steady, Pinto told investors at a conference.

That compares with a 10% in the second quarter, when revenue from equities jumped 21%, while fixed income climbed 5%.