Owner Balram Chainrai will take that step rather than risk the Premier League's bottom club being wound-up in the High Court on Monday when it faces a petition from the Government's Customs and Revenue department for unpaid taxes.
If the club goes into administration Portsmouth will lose nine points from a meagre total of 16 and face almost certain relegation.
A statement on the club's website read: "(Hong Kong) businessman Balram Chainrai, the owner of Portsmouth Football Club, has served notice the club will go into administration unless new owners can be found by Friday.
"Mr Chainrai and fellow investors from his Portpin investment vehicle are in London to continue talks with representatives of four different groups interested in buying the club but have had to reluctantly accept it is now unlikely a deal can be done before a winding-up hearing due to be heard in the High Court on Monday."
By going into administration the club would not be liquidated as the winding-up order would be suspended.
ATTRACTIVE PROPOSITION
According to media reports, Portsmouth have debts in the region of 70 million pounds.
The taxman is seeking at least 7.5 million pounds, the subject of the winding-up order.
Phil Hall, spokesman for Chainrai, told the website: "Administration would mean the club re-emerging as a healthy financial entity and it would then become an attractive proposition for a potential buyer who could invest new funds in rebuilding the club's future.
"We would like to ask the fans, the staff and management of Portsmouth Football Club for their support and patience should this step be taken as they believe it is the only route left open to them.
"The serving of this notice means the winding-up order is automatically suspended. It means the club is safe, it can fulfil its fixtures and as far as is possible it is business as usual," added Hall.
Hall said Chainrai would continue to finance Portsmouth until a buyer was found.
Chainrai is the club's fourth owner this season and pledged earlier this week he would do everything he could to save Portsmouth from going into liquidation next week.
