River Plate claim they have reached agreement with Ajax over the transfer of Mauro Rosales.
The forward said recently that he would like to secure a return to Argentina, following reports which claimed River were readying a bid for his services.
Things have accelerated, however, as River have now issued a statement saying the 25-year-old will make the move to the club next week.
River's players are due to return for training next week and they expect Rosales to be in situ for the start of pre-season.
The club have have also confirmed that midfielder Jesus Mendez is on his way to St Gallen after the two teams agreed a fee for his services.
River coach Daniel Passarella was initially reticent to sell Mendez, but the capture of Leonardo Ponzio allowed the clubs to push through the deal.