Fans from the Pompey Supporters' Trust (PST) had been hoping to take over the former Premier League club but their plan has been delayed by legal complications over ownership of the Fratton Park stadium. They now face a rival bid.
"We can confirm that we have received another offer for Portsmouth Football Club," said Trevor Birch, the joint administrator of the club.
"This offer has been made by Keith Harris, a former chairman of the Football League, together with Pascal Najadi, deputy chairman of the investment bank AIAK Group, and Alan Hitchins, a professional investor," he added in a statement.
Birch, who works for accountancy firm PKF, said he believed the offer could be completed without court approval, giving it a potential advantage over the PST bid.
Harris, chairman of London stockbroker Seymour Pierce, is prepared to meet the supporters to discuss a role for them in running the club. He has been involved in helping to arrange a number of soccer takeovers in the past.
However, the Trust said it wanted to pursue its plan to make Portsmouth the biggest fan-owned club in English soccer.
"PST can assure its supporters that its bid to buy Portsmouth Football Club is fully funded, ready to go and offers the best option for the creditors and for the long-term security of the club," it said in a statement.
"In addition PST can reveal we increased its bid for Fratton Park earlier this week to make our package even more attractive."
Portsmouth were in the Premier League as recently as the 2009-10 season but have become a byword for financial mismanagement in English soccer.
The team are facing relegation for a second successive season. They are second from bottom of League One and face a 10-point penalty for being in administration.