PRINCETON, N.J. -- Joe Viviano threw for two early touchdowns and scored on a 1-yard run in overtime to lift Harvard to a 23-20 win over Princeton in a battle of Ivy League unbeaten teams on Saturday.

After the Tigers opened overtime with a 25-yard field goal by Tavish Rice, Viviano had a big 15-yard run on third-and-3 to the Princeton 3.

Harvard (5-1, 3-0) took a 14-0 lead at the half as Viviano threw for a pair of touchdowns but the Tigers battled back and tied it at 17 with 48 seconds left on John Lovett's second TD run. The game-tying drive was set up by a great punt return by James Frusciante, who took it 30 yards to the Crimson 24 with 1:38 left.

Princeton (4-2, 2-1) had turned it over on downs after gaining 5 on fourth-and-6 with less than 2 minutes remaining, but the defense held, forcing a punt out of the end zone into the wind.

Harvard held the ball for almost 19 minutes longer but had four turnovers, including three Viviano interceptions.