The city of Chicago will close streets within a one-block radius of Wrigley Field leading up to Saturday's Crosstown Classic.
Security already is expected to be tight for the Cubs-White Sox game attended by NATO dignitaries, but NBC News reports the decision to close roads was made after concerns arose about protesters targeting the stadium.
NATO Secretary General Anders Fogh Rasmussen is scheduled to throw out the first pitch, and protesters reportedly could ramp up efforts in response to Cubs owner Joe Ricketts' campaign to defeat President Barack Obama by tying him to Rev. Jeremiah Wright.
NATO Night at Wrigley Field begins at 5:30 p.m., but a 7 p.m. concert at nearby concert venue Metro could snarl traffic even more.
A concert celebrating Woody Guthrie's birthday features Tom Morello, Jon Langford, Bucky Halker and Holly Near, among others. It's part of the year-long music series to attract a new generation of demonstrators.
The NATO Summit takes place Sunday and Monday.