The New York attorney general has asked a judge to order the testimony of Donald Trump's son in a probe of the president and his private businesses.
The investigation centres on whether Eric Trump and the Trump Organization improperly inflated assets.
Mr Trump, executive vice-president of the Trump Organization, dismissed the probe as "prosecutorial misconduct".
The investigation is one of several into the president's business dealings. Mr Trump denies any wrongdoing.
Last month, Manhattan District Attorney Cyrus Vance Jr, who is seeking the president's tax returns, said in court documents that his office was investigating "protracted criminal conduct" at the Trump Organization.
New York State Attorney General Letitia James launched the civil inquiry in March last year, after Mr Trump's former personal lawyer, Michael Cohen, testified before US lawmakers that the president had inflated the value of his assets to banks when seeking loans, and understated them to lower his taxes.
In addition to Eric Trump's testimony, Ms James's office is also seeking documents regarding four Trump Organization properties in Manhattan, upstate New York, Chicago and Los Angeles.
"Nothing will stop us from following the facts and the law, wherever they may lead," Ms James said in a statement. "For months, the Trump Organization has made baseless claims in an effort to shield evidence from a lawful investigation into its financial dealings. They have stalled, withheld documents, and instructed witnesses, including Eric Trump, to refuse to answer questions under oath."
The younger Trump was scheduled for an interview as part of the investigation last month, but abruptly cancelled, according to the court filings released on Monday.
"Without any basis, the [New York Attorney General] has pledged to take my father down from the moment she ran for office," Eric Trump wrote on Twitter, noting the order became public on the first day of the Republican National Convention.
Last month, the Supreme Court ruled that prosecutors could examine President Trump's tax returns.
The president has come under fire for not making his tax returns public like his predecessors. He accuses the investigations as a "witch hunt".