One of the businessmen whom the indictment of Mayor Eric Adams described as having made illegal donations to Mr. Adams’s 2021 campaign was expected to face a criminal charge and wishes to plead guilty, federal prosecutors said in a court filing on Monday.

The prosecutors have filed a notice of intent to charge the businessman, Erden Arkan, with conspiracy to commit wire fraud related to the illegal contributions, the filing said.

Nothing in the filing indicated that Mr. Arkan has been cooperating with the prosecutors in their case against Mr. Adams, who was charged with bribery, fraud and conspiring with Turkish officials to receive illegal foreign campaign donations. And there was some question of whether foreign money was involved in any of the actions Mr. Arkan is accused of taking, which may limit his ability to aid in the prosecution of Mr. Adams, a person with knowledge of the matter said.

The U.S. attorney’s office for the Southern District of New York unveiled the five-count indictment against Mr. Adams in late September, making him the first sitting mayor in the modern history of New York City to face criminal charges.

Mr. Arkan’s lawyer, Jonathan Rosen, with the Potomac Law Group based in Washington, D.C., declined to comment.

Although prosecutors have not indicated that Mr. Arkan is cooperating with the government, Alex Spiro, a lawyer for Mr. Adams, nonetheless said that he would be of little benefit in the case against Mr. Adams.