"He's going to come train with us. At that point we'll make an evaluation," Fire spokesman Daniel Jankowski said. "We are expecting him later this week."
The 32-year-old Salas, who also has played with River Plate of Argentina and Lazio and Juventus of Italy, already is in the United States and if he signs with Fire, would pair with Mexico's World Cup veteran Cuauhtemoc Blanco, who is to join the Chicago club in July.
Jankowski said he did not know how long the trial was scheduled for.
The Fire has scored only eight goals in nine games this season.
Horacio Matta, a retired Chilean tennis player who is promoting Salas' arrival to American soccer officials, said the player also has an offer from D.C United. Phone calls to the Washington club were not immediately returned.
Matta told the Santiago daily La Tercera that Salas may play one or two seasons in the United States.
After deciding not play during the Chilean Apertura season, Salas announced three weeks ago that he would return to the field - hopefully he said with Universidad de Chile. The announcement came as Universidad revealed it would emerge from bankruptcy - and therefore shed itself of court-appointed oversight, a deal that was completed Friday.