The Trump administration is considering naming Geoffrey S. Berman, a law partner of the former New York City mayor and ally of the president — Rudolph W. Giuliani, to assume the powerful position of United States attorney in Manhattan, according to two people familiar with the matter.

Mr. Berman emerged as the White House’s top choice for the job in a “proposed nominee” document that has been circulating between New York’s two Democratic senators, Charles E. Schumer and Kirsten Gillibrand, for their approval, said the two people, who spoke on the condition of anonymity because they were not authorized to speak about the matter. All nominees for United States attorney must be confirmed by the Senate.

BuzzFeed News first reported the development on Monday afternoon.

The United States attorney in Manhattan is among the top posts for federal prosecutors and has traditionally entailed overseeing international terrorism cases and criminal proceedings against Wall Street banks and bankers. The post has been vacant since the former officeholder, Preet Bharara, was fired by Mr. Trump in March.

Mr. Berman, 57, who does white-collar defense work at the law firm Greenberg Traurig, where Mr. Giuliani is a partner, was a federal prosecutor in Manhattan from 1990 to 1994, handling criminal cases that included tax, securities and computer hacking violations. From 1987 to 1990, he was an associate in the Office of Independent Counsel for Iran-contra. Neither he nor Mr. Giuliani returned phone calls on Monday seeking comment.