The 29-year old looked set to sign with Watford’s Championship rivals Reading but a bid from Pompey was also accepted by the Hornets.
"The Premiership side made their bid for the 29-year-old late on and it is now down to the player to decide upon a move to Fratton Park or Reading, after the Hornets had accepted an earlier bid from the Berkshire-based club."
However, Reading boss Brendan Rodgers is still hopeful the Royals will get their man.
"He was on his way to the club to sign the forms when he was told that Watford had accepted a higher offer from Portsmouth. I respect his decision to take stock by talking to them. He has turned down moves to other clubs because he wants to come here.
"His agent is away at the moment so communication is difficult. It happened late in the afternoon and I had to concentrate on this game, so we will see what tomorrow brings."