The Nerazzurri have been persuing the Brazilian for some time and Moratti insists the deal could still be done in the summer.
He told journalists: “This is a transfer that is not possible to do now.
"I think it will be easier to do next June. It's not an economic problem, but it's related to the player’s commitment to Corinthians."
Inter find themselves in fourth place in Serie A, nine points behind leaders Juventus while Paulinho was part of the Corinthians team that won the World Club Cup in December.
He has played eight times for the Brazil national team.