Economic activity in the U.S. manufacturing sector contracted at a slower rate in May, according to the Institute for Supply Management. Its key purchasing managers' index for manufacturing registered 49.6 in May, up from 48.6 in the previous month. However, only readings of more than 50 indicate expansion.

"In relative terms, May was down slightly from April as the rate of contraction in manufacturing slowed," said Norbert Ore, chair of the institute's manufacturing business survey committee. "Exports continue strong due to the weak dollar, without the weak dollar the story would be much more negative in manufacturing."

The employment portion of the index edged up to 45.5 in May from 45.4 in April.