The Fratton Park outfit felt they were close to signing the midfield pair earlier in the summer, but Wimbledon's financial troubles put their move in doubt.
Wimbledon's administrators were reluctant to authorise any move and now Pompey chief executive Peter Storrie has given up hope of signing the pair.
"The administrators at Wimbledon have a lock-out agreement with the prospective buyers of the club regarding the two players and as such there is nothing we can do," Storrie told the club's official website.
"It's very disappointing because both players would have give us so much but it has gone on too long and who knows how much longer before Wimbledon are taken out of administration."
