In 2016, President Erdogan asked then-Vice-President Joe Biden to remove Preet Bharara, the U.S. attorney for the Southern District of New York who would go on to indict Zarrab. Following continued lobbying by President Erdogan, Donald Trump did fire Bharara in 2017, and eventually replaced him with Geoffrey Berman. In late 2018, President Erdogan personally lobbied President Trump to drop further investigations into Halkbank, once in person during the G20 meeting in Buenos Aires (November 1, 2018), and once on a phone call (December 14, 2018); according to John Bolton, a first-hand witness of both events, Trump then agreed to have the investigations dropped. On December 14, 2018, the Department of Justice, then headed by Matthew Whitaker, notified Berman's office, that it would become more involved into the Halkbank investigation. Despite pressure from acting-Attorney General Whitaker and his successor, William Barr, to shut down the investigation, Berman and the SDNY office continued their investigation, believing that their case was strong. In June 2019, Barr summoned Berman to his office in Washington to push Berman to drop charges against the defendants, including Turkey’s former economy minister, Mehmet Zafer Caglayan, and terminate investigations of other suspected conspirators. Berman replied that this was unethical. After struggling with the legal technicalities of firing Berman, Barr announced on June 19, 2020, that Berman was "stepping down from his position" but also struggled to find a replacement on such short notice; for his part, Berman insisted that he had not resigned, and declined to leave office until his deputy Audrey Strauss, who planned to continue the investigation into Halkbank, had been installed.