According to reports in Portsmouth, PNE have been interested in the Republic of Ireland wideman since the start of the summer but are beginning to up their interest ahead of the transfer window deadline on August 31.
Curtis has been involved in every game so far this season for Pompey and has also been linked with Cardiff City and Blackburn Rovers - but his price tag seems to be putting off both clubs.
Bluebirds boss Mick McCarthy has spoken publicly on his doubts at whether they can meet the League One club's valuation.
The Lancashire Post understands that North End making a move for the 25-year-old is unlikely at this stage.
He is valued at £2m by his club and has not hidden that he would like to test himseld in the Championship, but he still has tow years left on his deal at Fratton Park.