Chainrai, who is seeking to purchase the club through his holding company Portpin, said eight days ago that he was withdrawing his bid in a public statement which criticised the Football League, administrators PKF and even the manager Michael Appleton.
That appeared to leave the Pompey Supporters Trust offering the club's last hope of survival. Hong Kong businessman Chainrai's company remains Portsmouth's biggest creditor and the PST urged him to negotiate with them over the value of the club's stadium, Fratton Park.
That remained a sticking point, and now Chainrai and Portpin are confident of reclaiming control of the troubled club, averting possible closure.
Portsmouth Supporters Trust are due to submit an updated offer for the club on Friday.
If Portpin have the backing of administrator Trevor Birch, they could scupper the supporters' hopes of bringing the former Premier League club under their own control.
"After many discussions with the related parties, including amongst others, the administrator, the Football League, the PFA, and officials from Portsmouth City Council, Portpin Ltd announces that it has decided to take action in order to avoid the imminent liquidation of Portsmouth FC," said Portpin.
"Portpin's offer will be in much the same form as previously with the club's current CVA being honoured and football creditors being settled in accordance with current agreements."
“We have been working with the Trust since Portpin's original offer was withdrawn and understand that the Trust is on track to submit a business plan and revised offer tomorrow [Friday]," said administrator Trevor Birch.
“We will assess its bid once it has been submitted and will then determine which offer provides the best deal for creditors, as is our duty as court appointed administrators.”