Tosic joined Pompey to play in their FA Cup win at Southampton but because of their financial plight, the Premier League held on to his registration.
"It is possible, we will see," Sousa told BBC Sport Wales after his side's 1-1 draw at Queens Park Rangers.
"He's training with us for the last week and it will be a possibility.
"Regarding our difficulties we have [with injuries] especially in our defence, what we need is fresh players without injuries who can help us."
Tosic was released from German side Werder Bremen and joined Portsmouth in February on a free transfer after the closure of the January transfer window.
He was an unused substitute in the FA Cup win, but because of the club's financial status, the Premier League ruled he was not allowed to play in the league so withheld his registration, preventing him from playing for anyone.
Tosic left Portsmouth despite still being registered, but now he has been cleared to join Swansea as an emergency loan following an appeal by the Serbian FA.
Swansea are looking to strengthen at the back with captain Garry Monk not fully fit from a calf injury, while Fede Bessone and Albert Serran are also out.
"We are waiting for players to return who are very close to help us in the last push of the season added," Sousa, who left Monk out of the draw with QPR.
"Garry Monk has had some problems this season and we are very happy because I can give him more time to recover completely to help us during the season.
"We can see a lot of teams with injury problems and we want to try to manage it the best we can."
Source: BBC Sport
Source: BBC Sport