The Croatian claims he has been told the striker will head up a major summer recruitment programme by the principality club's billionaire Russian owner Dmitry Rybolovlev, following their promotion back to Ligue 1.
Subasic told Croatian daily Sportske Novosti: "I'll tell you what I heard: Falcao is already 90 per cent Monegasque!
"He will appear in Monte Carlo in a few days and officially become our player.
"That's what they told us, with the only doubt being that he could sign for Real Madrid, which at the moment does not look likely.
"If he does not go to the Bernabeu, he will come to us in the principality. Let's wait for confirmation once it happens.
"I know the owner is not going to save, he has announced that in the summer he will spend more than 100million euros (£84.6m) on players."
Colombia international Falcao is third in the Primera Division scoring charts this season with 28 goals, behind only Lionel Messi and Cristiano Ronaldo, and also scored twice in last season's Europa League final.