Even at the stronger U.S. banks, troubled loans tied to cash-strapped consumers and struggling businesses are still rising quickly.

Wednesday's earnings reports from four large banks, including Wells Fargo & Co. (WFC), U.S. Bancorp (USB), SunTrust Banks Inc. (STI) and KeyCorp (KEY), largely tamed investors' growing hopes that the nation's levels of past-due loans are finally beginning to fall.

The most versatile banks, such as Wells Fargo and U.S. Bancorp, say they will continue to draw on a bevy of businesses - from mortgage refinancing to wealth management - to ride out the coming losses from loans gone bad. Smaller banks such as Keycorp, which expanded aggressively into now-sinking markets for commercial real estate, could yet face larger troubles in coming quarters.

Wells Fargo, which grew coast-to-coast last year after purchasing teetering rival Wachovia Corp., reported a blowout $22.5 billion in revenue for this year's second quarter.

But the San Francisco company's loan portfolios spooked investors. Loans Wells Fargo acquired from Wachovia are going bad faster than some investors had anticipated. Wells Fargo's total nonperforming loans, or those becoming uncollectable, grew 45% since the first quarter. Souring loans from Wachovia more than doubled to $5.6 billion.

"Even with that growth, we're still at a very low level of nonaccruals," or loans becoming uncollectable, Wells Fargo's Chief Financial Officer Howard Atkins told Dow Jones Newswires.

Shares in Wells Fargo were recently down 6% to $23.85 Wednesday.

U.S. Bancorp, likewise, reported impressive revenue, even as problems from loans - especially those tied to businesses - continued to rise.

In the second quarter, its revenue rose 7% from the first quarter to a record $4 billion - unusually robust growth for the middle of a recession.

But the Minneapolis bank set aside $1.4 billion to cover current and future loan losses, and Chief Executive Richard Davis said his company's loan loss reserves will continue to increase until losses start to decline.

Of U.S. Bancorp's commercial real-estate loans, more than 5% are now more than 90 days past due.

Shares in U.S. Bancorp were recently up 4% to $19.01.

Whereas consumer loans have been showing high numbers of delinquencies for many quarters, bankers and analysts widely suspect that loans made to businesses, and especially commercial real estate, are only now starting to show strains from the U.S. recession.

Keycorp posted a loss of $236 million after setting aside $850 million for current and future loan losses. The Cleveland bank's levels of nonperforming loans rose to 3.6%; in last year's second quarter, its loans approaching permanent loss stood at 1.6%.

Chief Executive Henry Meyer III said the company's results continue to reflect the weak economic environment.

Shares in Keycorp were recently up 5% to $5.07.

Atlanta-based SunTrust swung to a loss of $183.5 million, compared with year-earlier income of $504 million. It set aside less cash in the quarter for loan losses, even though troubled loans at the company are still on the rise.

Shares in SunTrust were recently up 5.2% to $15.97.

SunTrust's Chairman and Chief Executive James M. Wells III said the regional bank expects credit losses and non-performing loans to increase in the third quarter.

During a conference call with analysts, Wells cited "continued weakness in residential real estate-related and cyclically sensitive commercial exposures."

-By Marshall Eckblad and Matthias Rieker, Dow Jones Newswires; 212-416-2156; marshall.eckblad@dowjones.com

(Kerry Grace Benn and Brett Philbin contributed to this report.)