(Reuters) - Executives at some top U.S. banks cautioned against overly optimistic earnings projections and warned that the dealmaking environment was lagging expectations, clouding the outlook for a sector under stress since last year.

Their comments, made at a Barclays conference in New York, overshadowed concessions made by regulators over the "Basel Endgame" proposals - a set of highly contentious rules that would require banks to hold more capital.

Here is what the top executives had to say:

JPMORGAN CHASE ( JPM ):

"NII expectations are a bit too high. Next year, it's going to be a bit more challenging," said Chief Operating Officer Daniel Pinto.

"The U.S. economy, even though we see some slowdown, is doing is still okay, and the consumer is the main driver of that growth."

Investment banking fees in the third quarter could increase by 15%, he added, while markets revenue growth would be "flattish to slightly positive."

Pinto also warned of challenges in the commercial real estate industry, saying "we probably haven't seen the bottom of it."

CITIGROUP ( C/PN ):

"As I look at the (third) quarter, we're looking at investment banking fees to be up somewhere around 20% year over year," said Chief Financial Officer Mark Mason.

Annual net interest income (NII) - the difference between what the bank makes on loans and pays out on deposits - will end up "modestly" down from last year, he said.

"All of the spend growth is skewing from our largely affluent customer. There's a dichotomy, if you will, between the higher FICO score and the lower FICO score customers," Mason added.

Markets business revenue in the quarter could be down roughly 4%, he said.

BANK OF AMERICA ( BAC ):

Investment banking revenue in the third quarter is expected to be little changed from last year, CEO Brian Moynihan said. But middle market investment banking - involving transactions below $1 billion - has been growing at a double digit pace.

"The overall spending is locked in at good level. The employment is fairly stable. I worry more that if the Fed doesn't start to meet the expectations they read about in the paper, they could actually de-spirit the consumer," he said.

WELLS FARGO ( WFC ):

The bank maintained its annual NII forecast, but warned of pressure on lower-income customers.

"You're starting to see higher delinquencies in that cohort," said CFO Michael Santomassimo.

He also said that Wells Fargo ( WFC ) was comfortable with the allowance it had for its office loan portfolio. The bank could do more stock buybacks in the second half, "albeit at a slower pace," he added.

MORGAN STANLEY ( MS )

"M&A and IPO markets are still below what was expected. That is not going to change in the third quarter," said co-president Dan Simkowitz.

The bank continues to expect a "modest decline" in NII in the third quarter, but the markets business at the moment was "holding up," he said.

GOLDMAN SACHS ( GS ):

The challenging economic environment, particularly in the month of August, could lead to a 10% decline in revenue from the trading business in the third quarter, CEO David Solomon said.

Still, investment banking activity has improved and activity is "meaningfully better," he said.

(Reporting by Arasu Kannagi Basil and Pritam Biswas in Bengaluru; Editing by Sriraj Kalluvila)