New York's attorney general is seeking to question former U.S. President Donald Trump under oath as part of the state's civil fraud investigation of his namesake business, a person familiar with the matter said on Thursday.

The attorney general, Letitia James, wants Trump to sit for a Jan. 7 deposition as she probes whether the Trump Organization manipulated the valuations of its real estate properties, the person said, confirming a report in the Washington Post.

Representatives for Trump and his company did not respond to requests for comment. James' office declined to comment.

"This is not part of the criminal investigation," said a spokesman for the Manhattan District Attorney.

The civil probe is related to but separate from the more-than three-year criminal probe by Manhattan District Attorney Cyrus Vance of the Trump Organization's business practices, which James joined in May.

In July, the company and longtime Chief Financial Officer Allen Weisselberg pleaded not guilty to criminal charges in what a prosecutor in Vance's office called a "sweeping and audacious" 15-year tax fraud.

Trump, a Republican, has not been charged with crimes or accused of wrongdoing, and has called the probes politically motivated.

James also announced on Thursday that she was suspending her campaign to become New York's governor.

"I have come to the conclusion that I must continue my work as attorney general," James said in a tweet. "There are a number of important investigations and cases that are underway, and I intend to finish the job."

James, a Democrat, said she would run for re-election as New York's attorney general.

Vance, also a Democrat, leaves office at the end of the year following 12 years as district attorney.

The civil probe includes a focus on whether the Trump Organization overstated the value of some real estate assets to obtain loans and tax benefits.

James' probe began after Donald Trump's former personal lawyer, Michael Cohen, told Congress the former president also deflated other asset values to reduce real estate taxes.

Last year, Trump's son Eric, a longtime Trump Organization executive, was questioned in James' probe after initially resisting her subpoena.