Based on a Gallup poll of 600 owners nationwide, the San Francisco-based financial services firm's quarterly small-business optimism index fell to an all-time low, continuing a five-quarter slide. The index was launched in August 2003.

All six index components declined over the opening quarter, including measures for finances, cash flow, revenue, capital, hiring and credit.

"The nearly 50-percent drop in the index clearly reflects the intensified financial pressures small-business owners have felt over the last three months," Scott Andersen, the lender's chief economist, said in a statement.

Anderson said federal tax rebate checks mailed out earlier this month should give many businesses a boost by the third quarter. The checks are part of a $160-billion government plan to kick start the sagging U.S. economy.