Roma moved a point clear of Inter at the summit of Serie A after goals from Francesco Totti and Rodrigo Taddei earned a nervous 2-1 win at Parma yesterday.
Milan needed a late Ronaldinho penalty to edge past Fiorentina last night and strengthen their grip on third place in the table.
Ahead of Inter's away match in Rome against Lazio today, Totti struck after five minutes and Taddei doubled the lead with a quarter of an hour to go after Parma had bossed the match.
Davide Lanzafame's 81st-minute strike set up a tense finale but the Giallorossi, seeking their first scudetto since 2001, held on and with two matches to play will now be cheering on their city rivals.
"I told my players to battle and then see if the ball would run for us. Last week it went against us but today it went for us," admitted Roma coach Claudio Ranieri.
"I'm not thinking about Lazio but obviously if they play their part, tomorrow's game should be a tough one to win."
"Lazio are playing for survival so I expect them to play like Parma did against us today," said Roma midfielder Daniele De Rossi.
"We'll believe in the scudetto until the final minute of the season."
Parma coach Francesco Guidolin said his side did not deserve to lose: "We were technically superior so it's a hard loss to swallow. We must have made 30 crosses but couldn't convert most of our chances."
Ronaldinho inspired Milan's 1-0 home win over Fiorentina which practically assures them third spot and automatic qualification for the Champions League next season.
The Brazilian was in inspirational form, even if he only managed one goal, and that came from the penalty spot late in the game, but it was a crucial goal which takes the Rossoneri seven points clear of fourth-placed Sampdoria.
Fiorentina, meanwhile, saw their chances of qualifying for Europe next season ended by a defeat which leaves them seven points adrift of the top seven with just two games left to play.
Milan ended the game with 10 men when Massimo Ambrosini was shown a red card three minutes from time, but that did not spoil a particularly satisfying night for Milan coach Leonardo.
The build-up to the game had been overshadowed by a heated debate between Leonardo and the club's honorary president Silvio Berlusconi.
Milan created several chances but could not find a way through the Fiorentina defence before Per Kroldrup did them a huge favour by fouling Marco Borriello inside the penalty area.
Ronaldinho stepped up to at last get the better of Sebastien Frey in the 78th minute for what turned out to be the winning goal.