Donald Trump’s lawyers have said finding a bond to cover the $464m (£365m) judgment in his New York fraud case is a “practical impossibility”.
A judge ordered Mr Trump to pay the penalty in February for falsely inflating the value of his assets.
Mr Trump offered to post a smaller bond of $100m while he appeals, but that request was denied.
In a filing on Monday, his lawyers said they had approached 30 companies to back the bond without success.
“The amount of the judgement, with interest, exceeds $464m, and very few bonding companies will consider a bond of anything approaching that magnitude,” his lawyers wrote in the nearly 5,000-page filing.
They are asking a judge to put the judgement on pause while Mr Trump appeals against the decision.
“The practical impossibility of obtaining a bond interferes with defendants’ right to appeal,” his lawyers said.
Mr Trump’s two eldest sons also must 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 to cover the fine.
In the latest filing, the former president’s lawyers included an affidavit from a president of a private insurance firm, who said that “simply put, a bond of this size is rarely, if ever, seen”.
“In the unusual circumstance that a bond of this size is issued, it is provided to the largest public companies in the world, not to individuals or privately held businesses,” the lawyers also said.
Mr Trump’s team added that they had spent “countless hours negotiating with one of the largest insurance companies in the world” with no success.
They also said bond companies would not accept “hard assets such as real estate as collateral” for the bond, but only cash or “cash equivalents”, such as investments that can be quickly liquidated.
