Diego Milito scored twice to give leaders Racing Club a 3-0 win at Rosario Central and River Plate came from behind to beat Banfield 3-2 on Sunday, to take the Argentine league title race to the wire.
Lanus were also in with a chance of winning the title in a tight run-in to the Primera A championship. They were at home to Boca Juniors in Sunday's late match
With a round of matches to go, Racing have 38 points, after an 11-match unbeaten run including nine wins, and River 36, while Lanus face Boca with 33.
The final round of matches is expected to be postponed for a week so River can concentrate on the final of the Copa Sudamericana, South America's equivalent of the Europa League, against Colombia's Atletico Nacional, said sports daily 'Ole'.
Milito scored twice by running onto through balls and rounding the keeper in the final 25 minutes after Gaston Diaz had given them the lead in the 42nd.
"We're close to achieving what for us is a dream," Milito told reporters.
River, who relinquished top place in a 1-0 defeat at Racing last weekend, thanks to top players being rested for Thursday's Copa Sudamericana semi-final against Boca Juniors, won with two goals from substitute striker Fernando Cavenaghi at El Monumental.
It was only Cavenaghi's second appearance of the season after foot surgery, but he turned the match for River, coming on at halftime and equalising within nine minutes after Nicolas Bertolo had put Banfield ahead, just before the interval.
Winger Carlos Sanchez put River ahead three minutes later but they had Osmar Ferreyra sent off soon after, and conceded a penalty equaliser to Paraguayan striker Santiago Salcedo before Cavenaghi struck the winner from the spot in the 73rd minute.
Giving up a club record 31-match unbeaten run while they concentrated on reaching the Copa Sudamericana final, which they did beating Boca 1-0, has left River depending on a Racing defeat at home to Godoy Cruz and winning at lowly Quilmes to retain the league title.
"It's been a good week beating Boca and winning this hard match ... It's motivation for the final," Cavenaghi said in reference to the first leg of the South American final in Medellin on Wednesday.
