U.S. stock indexes were set for a muted open on Thursday as a surge in consumer prices in May fanned fears of early policy tightening by the Federal Reserve, while another report showed the labor market remained under pressure.

The Labor Department said its consumer price index increased 0.6% last month after surging 0.8% in April. In the 12 months through May, CPI accelerated 5.0% in its biggest year-on-year increase since August 2008. read more

The jump partly reflected the dropping of last spring's weak readings from the calculation. These so-called base effects are expected to level off in June.

"The numbers were slightly more than expected, but not way outside of the range ... I don't think this going to change the Fed's view of keeping rates very low," said Mark Grant, chief global strategist, B. Riley Financial.

S&P 500 futures dropped 0.2% immediately after the news, but turned course shortly after. They were last up 0.1%.

Focus will now be on the Fed's monetary policy meeting next week for more clues about the central bank's stance on tapering its massive stimulus.

The labor market and inflation are two key factors for the Fed to consider tightening, and while inflation has risen, recent payrolls data was underwhelming.

A separate report on Thursday from the Labor Department showed the number of Americans filing for jobless claims fell less than expected last week.

At 08:39 a.m. ET, Dow E-minis were up 64 points, or 0.19%, and Nasdaq 100 E-minis were down 37.75 points, or 0.27%

So-called "meme" stocks, which have dominated trading volumes in recent weeks,were again volatile before the bell, with recent retail target Clover Health (CLOV.O)flitting gains and losses. read more

GameStop Corp (GME.N), the stock most closely associated with the retail buying frenzy this year, fell 7.8% after it said it may sell new shares and said the Securities and Exchange Commission had requested documents related to an investigation into the Reddit rally that sent its shares up 1,600% in January. read more

Boeing (BA.N) rose 1.2% after sources told Reuters United Airlines (UAL.O) was in talks to place a multi-billion-dollar order for single-aisle jets potentially split between Boeing and Europe's Airbus (AIR.PA). read more

Ocugen Inc (OCGN.O) tumbled 26.7% after the drugmaker said it will not pursue an emergency use authorization for its COVID-19 vaccine candidate and would instead aim to file for a full U.S. approval of the shot. read more

Focus was also on a major infrastructure spending bill, talks over which hit a deadlock in the Senate.