Donald Trump cannot find a private company to guarantee the $464m (£365m) he has been ordered to pay in a New York civil fraud case.
The former president must either pay the full amount in cash or secure a bond in order to continue his appeal.
Mr Trump said that securing a bond of that size was “practically impossible”.
He faces the prospect of some of his real estate assets being liquidated unless he pays up.
For a fee, a bonding company would guarantee the full amount to the New York court.
In his statement, Mr Trump said that the bond he was asked to pay would be “impossible for any company, including one as successful as mine”.
“The bonding companies have never heard of such a bond, of this size, before,” he said.
Mr. Trump’s team spent “countless hours negotiating with one of the largest insurance companies in the world”, his lawyers wrote in a court filing.
The lawyers said they had approached 30 companies without success.
Mr Trump’s two eldest sons must also pay millions of dollars in the case.
Along with ordering Mr Trump to pay the penalty, New York Judge Arthur Engoron banned him from running any businesses in the state for three years after he found the former president falsely inflated assets to secure better loan deals.
A judge paused Mr Trump’s business ban last month but denied his bid to provide a smaller bond amount, $100m, to cover the fine.
Interest on the penalty is accruing by at least $112,000 per day until he pays.
The $464m judgment is not his only expense. He was ordered to pay $83m in January after losing a defamation case to E Jean Carroll, a woman he was found to have sexually abused. He has already posted a bond in that case.
