Donald Trump and his family business were found liable for fraud on Wednesday by a New York judge.
The decision was issued by Justice Arthur Engoron in relation to state Attorney-General Letitia James' civil lawsuit accusing the former US president of illegally inflating his assets and net worth.
James sued Trump in September 2022, accusing him and the Trump Organization of lying for a decade about asset values and his net worth to get better terms on bank loans and insurance.
She has said Trump inflated his net worth by as much as US$2.23 billion ($3.48 billion), and by one measure as much as US$3.6 billion ($5.6 billion), on annual financial statements given to banks and insurers.
The attorney-general has said assets whose values were inflated included Trump's Mar-a-Lago estate in Florida, his penthouse apartment in Manhattan's Trump Tower, and various office buildings and golf courses.
Lawyers for Trump and the other defendants did not immediately respond to requests for comment.
The court ruling is a setback for Donald Trump ahead of a trial in the case, which is due to start on Monday. Source: AAP / Alex Brandon
"He claims that if the values of the property have gone up in the years since the (financial statements) were submitted, then the numbers were not inflated at that time," Engoron wrote.
"He also seems to imply that the numbers cannot be inflated because he could find a 'buyer from Saudi Arabia' to pay any price he suggests."
A trial is scheduled for 2 October, and could last well into December.