The South Coast club will begin the coming campaign on minus ten points as a result of financial troubles, but are now working to release their remaining senior players
Birch has set the deadline of August 10 for the club to find new clubs for its remaining senior players, or reach financial compromise agreements with them.
The League One side have just three senior players left at the club, progress which has been praised by Birch.
"We've made encouraging progress," Birch told BBC Sport.
"There's still more work to do if we're to meet the conditions of the CVA and finalise the sale of the club," added Birch.
"Credit to the players that have left. It's not their fault that they were offered unaffordable contracts, but they've done what's best for the team, even though it meant taking a substantial hit themselves."
Kanu, who had previously lodged a claim for unpaid earnings which could have bankrupted the club, is now off Portsmouth's wage bill.
Administrators PKF also confirmed on Monday that the 35-year-old is still involved in a dispute over unpaid wages, causing the firm to file a submission to the Football League in order to find the easiest solution.
Out-of-contract Kanu is reportedly claiming £3 million in periods of unpaid wages since 2006, and Birch has requested that a tribunal intervene.
"There are three first team players still on the books," Birch added.
"Our priority is to continue to talk to them to negotiate the settlements that are needed to enable the club to survive. They know what's at stake and I trust that they will respond accordingly."
Greg Halford, Erik Huseklepp, David Norris and Luke Varney have all recently exited the club, leaving high-earners Dave Kitson, Liam Lawrence and Tal Ben Haim at Fratton Park.
There has been reported interest in midfielder Lawrence, while Ben Haim's agent claimed last week that the two parties were close to reaching a compromise agreement.
Balram Chainrai's Portpin and the Pompey Supporters Trust are vying for ownership of the troubled club, who will begin the new season on minus 10 points.