De Jong hasn't scored since joining Newcastle on loan from Borussia Monchengladbach in January, but Pardew believes that the forward's struggles could be down to a lack of match fitness following a difficult spell in the Bundesliga earlier in the season.
"It's about getting him back to match sharpness by giving him games and putting more fitness into him on the training ground," Pardew told reporters. "But at the end of this period, he'll have had three and a half months with us and he needs to be pretty close if we are going to sign him.
"This club needs strikers and I'm hoping he can tick a box for us between now and then.
"But I think it's important his all-round game improves from where he is right now."