
Both sides ended with 10 men a high-voltage game that left Inter unbeaten at the top on 61 points and a nine-point lead over Roma with 13 games left.
A classy first-half volley from captain Francesco Totti temporarily pushed Roma three points closer to their opponents, who appeared to be on the ropes when an injury on 65 minutes sidelined Brazilian defender Maxwell, who could not be replaced.
Inter had come close earlier as the post denied a spectacular volley from Argentinian Hernan Crespo, who in the first half acted as single striker due to the absences of Zlatan Ibrahimovic and Julio Cruz.
Coach Roberto Mancini at half time brought on David Suazo and the young Mario Balotelli for a three-pronged attack as Roma came close to beefing up their lead with hammering attacks and chances missed by Alberto Aquilani and Simone Perrotta.
The dismissal of French defender Philippe Mexes with six minutes left allowed Inter to increase their pressure until Argentinian captain Xavier Zanetti equalized with a drive from the limit of the area.
"Looking at how the game was going, it is good to have drawn," Mancini said. "We suffered when we had to, then we managed to draw."
Juventus are third on 48 points after drawing 0-0 with Torino on Tuesday and lead by four points Fiorentina, who Wednesday edged troubled Livorno 1-0 in a Tuscany derby.
AC Milan lie fifth after a 1-1 draw at struggling Catania and trail Fiorentina by two points in the race for the four available Champions League berths.
Udinese remain sixth despite a 2-0 defeat at lowly Parma, Sampdoria were held on 35 points as Atalanta in Bergamo beat them 4-1 win thanks to a brace from captain Cristiano Doni.
Genoa lie level with cross-town Samp after a 2-0 win over 10-man Napoli and Palermo beat Empoli 2-0.
Lazio beat 1-0 second-last Reggina and Siena also won 1-0 over bottom-side Cagliari.
By Alberto Cagliano, dpa