Eriksson insists Hart has the ability to become international number one - just two weeks after the young goalkeeper conceded six goals at Chelsea.
After the latest at Fratton Park in the Premier League, Eriksson was asked if he could see Hart in international colours - and his reply was unequivocal.
"Yes, he can do it," said the Swede.
"He is an under-21 already, and that usually means you can step up.
"He made some great saves today and yet he's still not happy with himself. I know why - it is his kicking."
But Eriksson, who has been linked with a new wave of signings in January but denies any plans are in progress, said: "I've told him not to blame himself for that [the landslide of goals at Stamford Bridge].
"We had 10 other players on the field who should have defended better. But I could understand why he was down.
"It is not easy to come back after conceding six in a match. But he's done it, and we were a different side today to the one against Chelsea. We had to be.
"Sooner or later I have to decide whether we need another goalkeeper. I think it will be later. But our season is going well so far, and we can't complain about our home form. Away it has not been so good - but this, today, was much better.
"We could have won - but so could Portsmouth. They had chances, and we had chances. Darius Vassell, I thought was unlucky with one."