A private trade group said the U.S. manufacturing sector expanded in May, marking the 10th consecutive month of growth.

The Institute for Supply Management, a trade group of purchasing executives, said Tuesday its manufacturing index dipped to 59.7 in May from 60.4 in April. A level above 50 indicates expansion.

"We haven't lost much in the way of momentum," said Norbert Ore, chairman of the ISM's manufacturing survey on a conference call.

"The manufacturing sector continues to move ahead."

Economists polled by Thomson Reuters had expected the index to dip slightly to a reading of 59.

New orders, a gauge of future production, were unchanged at 65.7. Export orders grew despite conners about growth in Europe and Asia.

That's "unquestionably a positive," wrote Dan Greenhaus, chief economic strategist with Miller Tabak & Co.

ISM said its employment index, which measures employers' willingness to hire, rose 1.3 percentage points to 59.8.