U.S. stock market index futures pared their gains as European Central Bank chief Mario Draghi spoke, after the central bank kept its interest and deposit rates unchanged.
In a press conference, Draghi said the ECB is "technically ready" to lower the bank's deposit rate into negative territory for the first time, which would mean the central bank would charge commercial banks for holding their money overnight, but ruled it out for the time being.
"That's an indication that Draghi feels that the problem of lending is going to continue to dampen the outlook for a comeback anytime soon," said Peter Cardillo, chief market economist at Rockwell Global Capital. "The risk in the euro zone remains to the downside."
The ECB left its main interest rate unchanged at a record low 0.50 percent and said the euro zone is on track for a "very gradual recovery" later this year driven by the central bank's loose monetary policy and demand from abroad. (CNBC.com is streaming this event live.)
"The Governing Council continues to see downside risks surrounding the economic outlook for the euro area," Draghi added. "They include the possibility of weaker-than-expected domestic and global demand and slow or insufficient implementation of structural reforms in euro area countries."
European shares also cut their gains following the press conference.
On the economic front, jobless claims dropped 11,000 to a seasonally adjusted 346,000, according to the Labor Department. Economists expected a reading of 345,000. Earlier, executive recruitment firm Challenger, Grey & Christmas' said corporate job cuts declined again in May.
Investors will be paying close attention to Friday's government jobs report. Employers are forecast to have added 170,000 jobs to their payrolls last month, slightly up from April's 165,000 count, according to a Reuters survey. The unemployment rate is seen holding at an almost 4-1/2 year low of 7.5 percent.
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Employment is a key indicator for the Fed, and Chairman Ben Bernanke has indicated the central bank could start tapering off its $85 billion bond purchases if the jobs market shows consistent improvement.
"The weaker ADP employment survey and ISM (Institute of Supply Management) non-manufacturing employment sub-component, released on Wednesday, were both consistent with U.S. employment growth slowing modestly in May," said Emily Nicol, an economist at Daiwa Capital Markets, in a research note on Thursday.
(Read More: Traders Confused: Is Jobs Market Improving or Not?)
In a scratch poll by CNBC of money managers, economists and strategists on Wednesday, around 35 percent forecast the Fed would start winding down its bond purchases in September, while 23 percent expected the Fed to wait until January 2014. Only 3.8 percent expected tapering off to start next month.