"While on the runway our flight made contact with some seagulls prior to takeoff," United spokeswoman Robin Urbanski said.
Flight No. 1220, scheduled to depart at 7:12 a.m., was traveling at about 120 knots, or about 138 mph, when it hit the birds, Urbanski said.
She said the pilot was able to stop the plane safely, and shut off an engine as a precaution.
Airport spokesman David Vossbrink said no one was injured but that the event was "sufficient to cause the pilot to cancel the flight and go back to the terminal."
It was almost exactly one month ago that a U.S. Airways flight made an emergency landing in New York's Hudson River after the plane struck a flock of geese, disabling both of its engines.
Aviation officials have said it is relatively common for planes to strike birds, and that most such incidents are minor.
Urbanski said passengers on today's flight are being booked onto another flight later in the day.