By Ann Saphir

May 1 (Reuters) - Borrowing by small U.S. firms stalled in March, as business owners remained cautious about investing amid policy uncertainty, data released on Monday showed.

The Thomson Reuters/PayNet Small Business Lending Index for March registered 134, down 1 percent from last March. The index was up 4 percent from February, which had four fewer working days.

Movements in the index typically correspond with changes in gross domestic product growth a quarter or two ahead. The U.S. economy grew at a 0.7 percent annual pace in the first quarter, figures released on Friday showed, the slowest in three years.

Bets that U.S. President Donald Trump's planned tax cuts will boost corporate profits have lifted U.S. equities since his November election, but small businesses appear to be keeping their powder dry, said Bill Phelan, PayNet's chief executive and founder.

"They didn't get sucked into all the euphoria of public markets; they are just, 'Wake me up when we are there,'" Phelan said in an interview. "There's not going to be any kind of enthusiasm."

Borrowing by healthcare companies was down 13 percent in the month, he said, probably reflecting worries about prospects for other Trump policies, including a so-far unsuccessful bid to repeal and replace the Obamacare healthcare law.

Small business borrowing is a key barometer of growth because small companies tend to do much of the hiring that drives economic gains.

Meanwhile, a separate barometer of small companies' financial health suggests companies are not avoiding new debts because of troubles paying off old ones. The share of loans more than 30 days past due was 1.68 percent in March, unchanged from February, PayNet data showed.

PayNet collects real-time loan information such as originations and delinquencies from more than 325 leading U.S. lenders. (Reporting by Ann Saphir; Editing by Jonathan Oatis)