Dundee United's controlling Thompson family has decided that it can no longer continue to fund the Tannadice club with its own money.
It follows a decision by United's bankers that all the £2.8m transfer fee from the sale of David Goodwillie must go to reducing the club's debt.
United had hoped to add to their squad.
But one source at Tannadice told BBC Scotland that the club had been told they had to sell another player before the transfer window closes.
Manager Peter Houston had realised that most of the money from Goodwillie's switch to Blackburn Rovers would be taken by the bank.
However, he had hoped to receive some cash to bring in players who would not command a transfer fee.
Speaking after his team's 1-0 home defeat by Dunfermline on Saturday, he said: "Unfortunately, with the state of the club, we can't bring anybody in.
"The best thing for me would be to get someone who could play in the wide position and put crosses into the box.
"But finance dictates a lot things and it's unfortunate that the bank are turning the screw on the chairman and the football club.
"If we don't get anybody in before the window closes we'll just need to work with what we've got.
"It's more important that Dundee United are here as a football club than Peter Houston getting all the players he wants."
United have lost a number of first-team players during the summer.
And, with season ticket sales down by 18% this season, costing the club around £200,000 in lost income, the Scottish Premier League club has now been enveloped in further financial uncertainy.
The late Eddie Thompson put millions of his own money into the club, but it is believed that current chairman Stephen Thompson and his mother, Cath, who owns the shareholding, feel they can no longer sustain previous levels of investment.