After gaining renewed strength in recent months, confidence in the economy among the nation's small-business owners plummeted in September, driven down by growing concerns over the financial market crisis, Discover reported this week.

Of 1,000 owners surveyed nationwide, 51 percent said conditions for their businesses were getting worse, up from 44 percent in August, the credit card firm said. Another 73 percent said the U.S. economy was getting worse, up from 60 percent. Only seven percent said they felt the economy was improving, an all-time low for the monthly surveys.

More owners said they were taking less money home from the business, the survey found. Though accessing credit was getting tougher, less than a third of respondents said they've been forced to borrow money to pay the bills.

"Even though we had two months of rising confidence, this month's drop isn't surprising given the constant stream of uninspiring news about the housing and lending markets," Ryan Scully, director of Discover's business credit card, said in a statement.