On Thursday, Turkey’s foreign minister, Mevlut Cavusoglu, raised concerns about the Zarrab case during talks in Ankara with the United States secretary of state, Rex W. Tillerson, The Associated Press reported.

Mr. Cavusoglu claimed that Mr. Zarrab, and a Turkish banker who was arrested this week on related charges, were the targets of a politically motivated case, The A.P. reported. Mr. Cavusoglu said that Preet Bharara, the former United States attorney whose office last year charged Mr. Zarrab, “opposes” the Turkish government, The A.P. said.

Asked for comment, Mr. Bharara said in a brief statement, “I am not going to comment on false and silly political propaganda by a foreign official regarding a case that I no longer oversee.”

Mr. Bharara was dismissed this month by the Trump administration after he refused to tender his resignation.

The office of Joon H. Kim, the acting United States attorney in Manhattan, declined to comment on Thursday, as did Mr. Brafman. A spokeswoman for Mr. Giuliani’s law firm, Greenberg Traurig, said, “Because of client confidentiality, we cannot discuss any details of this matter.” Mr. Mukasey’s office declined to comment.

The letters to Judge Richard M. Berman of the Federal District Court came after prosecutors asked for a hearing on whether Mr. Giuliani’s and Mr. Mukasey’s retention posed a potential conflict of interest in the case. They said Mr. Giuliani’s firm as well as Mr. Mukasey’s firm, Debevoise & Plimpton, had each represented banks that were believed to be victims in the case. Mr. Brafman had argued that a hearing was not necessary.

Mr. Zarrab, 33, was born in Iran and moved to Turkey as an infant, and has dual citizenship. Prosecutors say he conspired to facilitate millions of dollars in transactions on behalf of Iran and other sanctioned entities through the use of false documentation and front companies. He was also charged with conspiracies to commit bank fraud and to commit money laundering. He has pleaded not guilty.

His case has been closely watched in Turkey, where he was detained in 2013 during a corruption investigation of businessmen with close ties to Mr. Erdogan, then the prime minister. He used his wealth and influence to be released from prison in Turkey, prosecutors said last year in their successful argument that he be denied bail pending his trial, which is scheduled for August.