The move will mean the automatic deduction of nine points to almost certainly seal their relegation from the Premier League to the Championship at the end of the season.
In a statement on the club's website, Phil Hall, spokesman for the owner Balram Chainrai said: "There is now only a short window of opportunity for buyers to come in with a credible offer. We have to be realistic and having the club wound up is not an option as far as we are concerned.
"The partners have put 17.0 million pounds of their own money into the club and have a responsibility to ensure Portsmouth Football Club survives.
"Administration would mean the club re-emerging as a healthy financial entity. The club 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 south-coast club, who face a winding-up petition from the British government's Revenue and Customs department in the High Court on Monday, are expected to become the first Premier League side to go into administration.
According to media reports based on court documents, the club are 70 million pounds in debt and have been threatened with being wound-up by the tax department who have filed in court for 7.5 million pounds in unpaid taxes.
Chainrai said on Tuesday he would place the club in administration unless a buyer came forward by Friday but that is now unlikely to happen.
Portsmouth currently have 16 points from 26 matches and are eight points from safety. After the points deduction they would have seven points and be 17 from safety with only 12 matches remaining.
Manager Avram Grant, who replaced Paul Hart in November, told Sky Sports News he had "more or less" been told the club would go into administration on Friday.
"I feel very sad, very angry, but I need to understand more of the situation. I came to do a football job here and at every step, I couldn't do the job, I am very sad for me and for everybody."
