U.S. credit card users fell further behind on their bills in the three months through June, according to a new report from the Federal Reserve Bank of New York, an ominous sign for lenders.

The rising delinquencies occurred as total consumer credit card debt in the U.S. rose 7.5% to $784 billion amid a broader increase in household borrowing. The percentage of credit card balances at least three months behind on payments rose 21 basis points from a year earlier to 7.38%.

That's still lower than levels in the more immediate aftermath of the 2008 financial crisis, reflecting labor market growth and years of lower interest rates that benefited many U.S. consumers, but compounds concerns about the economic recovery's failure to reach all sectors of the economy. It may also complicate the Federal Reserve's decisions about whether to raise short-term interest rates for the third time this year and when to begin paring its $4.5 trillion balance sheet.

Some members of the central bank's monetary policy committee have already expressed reservations about lackluster inflation, stubbornly shy of a 2% target, and noted that a jobless rate of less than half its 2009 peak has failed to yield significant wage growth.

"The current state of credit card delinquency flows can be an early indicator of future trends and we will closely monitor the degree to which this uptick is predictive of further consumer distress," Andrew Haughwout, a senior vice president at the New York Fed, said in a statement.

The late payments increased the most for cardholders with credit scores below 660, a level that indicates higher risk to lenders, suggesting that "consumer distress appears to be limited to those borrowers," Haughwout and a team of researchers said in a New York Fed blog post. That means the increasing delinquencies may be related to a relatively recent move by lenders to ramp up loans to higher-risk borrowers, many of whom struggled to obtain credit as banks tightened standards following the 2008 financial crisis.

Indeed, charge-offs have risen at large credit-card lenders like Synchrony Financial (SYF) and Capital One Financial (COF) .  Synchrony's charge-offs, or debt written off as uncollectible, rose 91 basis points to 5.42% in the three months through June, although CFO Brian Doubles said on a July earnings call that it would likely decline this quarter.

"Late payments are slowly rising but they're still low by historical standards," Matt Schulz, a senior analyst for CreditCards.com, said in a statement.

"That means that most people are handling their card debt well even as it grows," but the trend won't last forever, he explained. "Even if you feel your debt is manageable right now, know that you could be one unexpected emergency away from real trouble. Get that debt paid down while things are good so you can be better prepared if things turn for the worse."

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Editors' pick: Originally published Aug. 15.

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