Donald J. Trump on Wednesday lost his initial bid for a New York appeals court to pause the more than $450 million judgment he faces in a civil fraud case, a decision that could expose him to financial peril.

Mr. Trump’s lawyers had asked the appeals court to allow him to post only a $100 million bond — a promise from an outside company that the judgment eventually will be paid — because securing one for the full amount was “impossible,” they said.

A single appellate court judge assigned to consider Mr. Trump’s request, Anil Singh, turned him down on Wednesday. Mr. Trump will try again next month with a panel of five appellate court judges, but for now, the former president is still on the hook to post a bond for the full amount of more than $450 million. And any company providing one would probably require him to pledge cash and other collateral that he does not yet have.

If Mr. Trump fails to secure the bond, the New York attorney general’s office, which brought the case accusing him of fraudulently inflating his net worth, can collect the $454 million from him. The attorney general, Letitia James, is expected to provide Mr. Trump a 30-day grace period, which will expire on March 25, at which point she could move swiftly to seize Mr. Trump’s bank accounts and perhaps take control of his New York properties.

The $454 million judgment was levied by the trial judge in the fraud case, Arthur F. Engoron, who also imposed a range of other punishments on Mr. Trump and his family business. They include a prohibition on obtaining a loan from a New York bank for three years and a ban on running a company in the state during that same period, restrictions that are complicating Mr. Trump’s effort to line up a bond.

“The exorbitant and punitive amount of the judgment coupled with an unlawful and unconstitutional blanket prohibition on lending transactions would make it impossible to secure and post a complete bond,” Mr. Trump’s lawyers wrote to the appeals court.