The US manufacturing sector struggled to grow in May, underlining worries over the pace of economic recovery.
The Institute of Supply Management's manufacturing activity index fell in May to its lowest since June 2009.
Markit's May purchasing managers' index rose, but the increase was too small to point to a sector revival.
The BBC reports both are closely-watched and sentiment was dampened on Wall Street.
The ISM index of manufacturing activity fell to 49 last month from 50.7 in April.
The reading was the index's lowest level in almost four years, and the first time the index has dipped below 50 since November. A reading under 50 indicates a contraction.
The US economy grew at an annualised rate of 2.4% in the first three months of the year.
The BBC reports economists widely expect growth to slow again in the next three months, due in part to the slowdown in the manufacturing sector.