A source from the Norwegian club told the Evening Chronicle: "What is interesting is that Newcastle are still following Skjelbred and are preparing to lodge a £4.5m bid for him if their bigger transfer targets slip out of their hands.
"Which is also why Skjelbred is putting off signing a new deal with Rosenborg. He does not want to make things messy if Newcastle or another club he might find interesting comes in for him before the end of the transfer window."
Skjelbred has three caps for Norway and feels he has nothing more to prove in his country's native Tippeligaen.
The Chronicle reported on July 4 that United had been scouting the player, and his agent said: "All the clubs from the big leagues have been watching him.
"So far what I can say is that nobody from Newcastle has come to me.
"There has been no contact in that way yet.
"He is very ambitious, and if Newcastle came to us with an offer then we would have to seriously consider it."