Markit Economics released its preliminary services purchasing managers' index (PMI) for the U.S. on Tuesday. The U.S. preliminary services purchasing managers' index (PMI) rose to 52.1 in April from 51.3 in March. Analysts had expected the index to rise to 52.3.

A reading below 50 indicates contraction in economic activity.

The increase was driven by a marginal growth in new work. Job creation slowed to the weakest level since October 2015.

"The upturn in the rate of growth of business activity and increased inflows of new orders suggest the economy should see GDP rise at an increased rate in the second quarter, but growth is clearly far more fragile than this time last year," Markit Chief Economist Chris Williamson said.