U.S. companies borrowed 4% more in August to finance their investments in equipment compared with a year earlier, industry body ELFA said on Friday, while raising doubts over the sustainability of this growth amid slowdown fears.

The companies signed up for $8.8 billion in new loans, leases and lines of credit last month, compared with $8.5 billion a year earlier, according to the Equipment Leasing and Finance Association (ELFA). Borrowings were up 5% from January.

"With the Fed's most recent 75-basis-point jump in short-term interest rates, and the prospect of a hard landing, time will tell whether — and to what extent — these same business owners continue to grow and invest in equipment," ELFA Chief Executive Ralph Petta said in a statement.

ELFA, which reports economic activity for the nearly $1-trillion equipment finance sector, said credit approvals totaled 75.2%, down from 78% in July.

The Washington-based body's leasing and finance index measures the volume of commercial equipment financed in the United States.

The index is based on a survey of 25 members, including Bank of America Corp, and financing affiliates or units of Caterpillar Inc, Dell Technologies Inc, Siemens AG, Canon Inc and Volvo AB.

The Equipment Leasing & Finance Foundation, ELFA's non-profit affiliate, said its confidence index in September stood at 48.7%, compared with 50% in August. A reading above 50 indicates a positive business outlook.