And the former Football League chairman believes he can help save the stricken club who are in danger of liquidation.
"I should first make clear that we would not have pursued this investment without sound financial backing and the right senior management," Harris said in a statement.
"Secondly, I should also be very clear that we will not be carrying forward any legacy issues associated with the recent past. We will be starting with a financial clean sheet.
"Personally, I had signalled to my colleagues at the investment bank Seymour Pierce that I intended over a reasonable period of time to broaden my career interests and, therefore, I stepped down from the bank's operating board on 17 May 2011, nearly two years ago. Over that period I have reviewed a number of opportunities in football. This, to me, became the stand-out opportunity.
"We have the people with the ability to achieve solid progress over the next few years and bring much needed stability to the club. No-one on the new team underestimates the scale of the task that lies ahead.
"We understand, of course, that the fans, the commercial partners and the staff will have many questions and we will address these over the immediate period ahead."
Harris is proposing to become the club's new chairman with former Swansea City chairman Steve Hamer appointed as managing director and John Redgate their chief financial officer.
The PST have been approved by the Football League as well as the club's creditors.
But their takeover is conditional on them taking control of the club's Fratton Park stadium.
It is controlled by the club's former owner Balram Chainrai, who is owed £12m by Pompey and holds the stadium as security via a fixed charge.
The PST had offered Chainrai £2.75m for the ground but the Hong Kong businessman has so far refused to sell. Following Thursday's revelation of a rival offer the PST themselves released a statement saying they had increased their offer for Fratton Park to £3m -
" to make their package even more attractive".
Keith Harris reveals interest in Man Utd takeover
PKF are attempting to force the sale of Fratton Park through the High Court, as well as seek an independent valuation, although the hearing has been adjourned several times. The latest hearing is set for 14 February.
"As officers of the Court, the administrators are charged with securing the best return for all creditors and therefore have to consider the offer," added the statement.
"We will need to discuss the terms of the deal with the PFA (Professional Footballers' Association) and the Football League, and also plan to consult the Creditors' Committee as a matter of urgency.
"This has been a complex administration and we are doing all we can to resolve the situation as quickly as possible. We will provide an update as soon as we have further news."
The PST remain bullish that their takeover will go ahead and added: "Our bid is complete and ready to go. What we need is a complete break from the past."
Trust spokesman Colin Farmery added on BBC Radio Solent on Thursday: "We just want to get on and do the deal now.
"Our bid is fully funded and we are the preferred bidder. The Supporters' Trust want to put money into the club, we intend to buy Fratton Park and ensure the club owns its own stadium.
"It has got to be sorted and the thing is there is a solution. The solution is our bid, it's ready to go."
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