Kanu has accused Pompey of ‘utter contempt and disrespect’ and pledged to continue his training ground no-show.
And, in a shock new move, the veteran has lodged a claim against the Blues with the Football League which runs into millions of pounds.
If accepted, funds will come out of crucial distribution payments pinpointed to keep the club alive.
Pompey’s longest-serving player, who has failed to attend the first three days of pre-season training, is currently in Nigeria.
Kanu’s barrister, Samuel Okoronkwo, claims the 2008 FA Cup hero has taken the stance over his treatment by the club.
Administrator Trevor Birch has been in prolonged talks regarding a compromise agreement to settle the remaining 12 months of the 35-year-old’s contract.
He has not played for the Blues since October 2011 and the club are desperate to drive down the £9.5m wage bill and stave off the threat of liquidation.
However, the situation has come to a head after Kanu failed to turn up for pre-season training on Monday.
On Tuesday evening his barrister lodged a claim with the Football League under the football creditors’ ruling.
And Okoronkwo insists his client is entitled to the money, which is earmarked to keep the club running through administration.
He said: ‘I have been given authorisation to speak on Mr Kanu’s behalf. He feels very aggrieved.
‘He has regrettably been forced to serve the requisite notices of breaches of contract by the club, both historically and presently.
‘This naturally leads to the Football League.
‘He has been playing and scoring goals for Portsmouth for six years, sometimes playing through injury. Now he is being treated like this.
‘He has lost millions of pounds since 2006 through genuine contractual obligations but has been prepared to wait.
‘Now they are threatening breach of contract.
‘Mr Trevor Birch attended my office in May and said he did not want Kanu to stay at the club, which I found surprising, especially having waived millions of pounds he is entitled to.
‘Then I received an e-mail on Saturday stating if he did not turn up for training on Monday he would be held in breach of contract.
‘I had already told the club he was doing a job for the Nigerian national team so was unable to.
‘Mr Birch also wanted a compromise agreement to be reached on the Sunday. That was entirely unrealistic.
‘The club have not shown themselves to be worthy to reach any agreement with him through the utter contempt and disrespect they have shown.
‘Kanu has been willing and able to play and trains every day.
‘But he finds himself unable to return to the club. He wants to be treated respectfully and, on that basis, cannot return to training.’
Kanu is not alone in approaching the Football League directly seeking payment of monies owed.
Ex-directors David Lampitt, John Redgate and Nick Byrom did so in May, diverting vital distribution funds required by Pompey.
Birch is continuing to talk to Okoronkwo to reach a deal as he battles to slash the wage bill to secure a takeover.
The administrator has declined to comment on the latest developments as he does not wish to criticise players.