The 29-year-old has scored four goals in his five matches for Koeman's side following his £9m move from Feyenoord in the summer.
Pelle was named on the pre-squad list for Antonio Conte's side's matches against the Netherlands and Norway, and the Dutchman feels that it is only a matter of time before Pelle makes the breakthrough into the full squad.
Koeman told reporters: "He was one of the pre-list of the Italian national team. Of course, that gave him the support and confidence that he is doing well.
"He is in the head of the coach of the national squad, because you don't put anybody on the pre-list if you don't think about that player.
"When he is playing like he is now then maybe he is a possibility. If you show that quality in the Premier League of course you are good enough to be part of the Italian squad."
Southampton face Swansea City in their Premier League clash later today.