The ADP National Employment report showed U.S. private employment rose by 145,000 jobs last month, compared with economists' projections of an increase of 200,000 jobs, adding to recent signs of a cooling economy.
Traders' bets of a pause by the Fed in May shot up to 60.8%, while odds of a 25-basis point interest rate hike fell to 39.2%, according to CME Group's Fedwatch tool.
Defensive stocks such as healthcare (.SPXHC), utilities (.SPLRCU) and consumer staples (.SPLRCS) were in the green among major S&P 500 sectors.
All eyes are now on the non-farm payrolls data for March, a more comprehensive employment report, that is due on Friday for further clues on the state of the labor market.
Both the benchmark S&P 500 and the tech-heavy Nasdaq (.IXIC) are now on track for their first weekly declines in four in the holiday-shortened week.