Apparently Viduka is off to Croatia (his birthplace) after being let go by Newcastle.
But the deal to take him to Fratton Park, although facing problems, is not yet dead.
The £60m takeover by Sulaiman Al Fahim has hit a cash crisis with present owner Sacha Gaydamak needing to pay back a £20m loan next week.
Gaydamak may put the club into administration.
Hart said: "There appears to be a problem.
"Mark Viduka and I have spoken a lot. His fitness would be a concern but he's a quality player."
Viduka has had no pre-season training, has not featured n any games (for anyone), and has been training with Weightwatchers.