River's second leg showdown at home to Boca was rearranged for Sunday but Alejandro Dominguez, president of South American soccer's governing body, CONMEBOL, said: "We need to allow both clubs to recover so, with this in mind, we will be postponing the match.

"It's a disgrace we are talking about this because of a few hooligans. This is not football -- it's not what we want. We understand that the players are professionals, who live, work and give their everything on and off the pitch.

"Today, we find ourselves with a playing field which is not level. One team was attacked and we need to think of a fair final. We need to send out a signal that the organisation is here to produce a sporting spectacle.

"We don't want any excuses and, for this, CONMEBOL believe there is not a level playing field for the match to be played. The presidents of both clubs are invited to the CONMEBOL offices to discuss the rearrangement. The match will be played. It is not a Boca statement, it is a presentation and we are being sensible. It is a postponement. The final has not been suspended.

"Boca's request prompted the change. Today, we have new facts and medical evaluations which do not guarantee safe conditions."

No date has yet been specified for the crucial second leg to be played. A meeting will take place on Tuesday to determine the date of the final.

River Plate fans attacked the Boca Juniors team bus on Saturday, injuring players as they travelled to the stadium in Buenos Aires, Argentina. Police used tear gas and pepper spray to control the violence and Boca captain Pablo Perez and midfielder Gonzalo Lamardo were taken to nearby hospitals after suffering injuries.