The 10-year Treasury note futures were also trading flattish at the open. Nasdaq 100 e-minis, meanwhile, were up 0.09 percent on volume of 2,417 contracts, while the Dow e-minis were up 0.13 percent, with 1,248 contracts changing hands.

Investors had been bracing for updated news on Mueller's investigation.

U.S. Macro Strategist Alastair Williamson, founder of S.B.A. LLC, said e-mini S&P 500 Futures had a "muted response on the report, overshadowed by a flurry of information last week that pointed to another growth scare in Europe, Asia, and the (United States)."

Williamson said it seems the Mueller report "is a 'nothing burger' for bulls." He added: "Investors should revert their attention to a deterioration in global macro and be cautious that monetary and fiscal policy are currently unable to extend the global boom, as the synchronized slowdown festering in Europe, Asia, and the U.S becomes more severe into the second quarter."

(Reporting by Trevor Hunnicutt and Jennifer Ablan; Editing by Peter Cooney and Chris Reese)