"Bharara has been behind that process… This process is a political one.. because former prosecutor Bharara has had close ties with Fethullah terrorist organization," Cavusoglu said.
The foreign minister added that the Turkish government had been sharing "comments and opinions" with the US authorities since the day the arrest was made.
On Wednesday, Cavusoglu said that the Fethullah Terrorist Organization (FETO), believed to be the organizer of the thwarted July coup in Turkey, could be behind the detention.
Earlier in the day, the Turkish foreign minister met US Secretary of State Rex Tillerson, who is currently on a visit in Ankara.
Bharara initiated the case against Zarrab, a dual citizen of Turkey and Iran, who was arrested in March 2016 on suspicion of laundering money for Iran.
Bharara was fired in early March 2017, despite claiming soon after the 2016 presidential elections that Donald Trump, who was the president-elect at the time, asked him to stay on. His dismissal came as part of a larger effort by the new administration to start with a clean slate as 46 US state attorneys were asked to resign.
The United States has been imposing economic sanctions on Iran since 1979. This policy has been used to curb Iran's nuclear program. On July 14, 2015, Iran and the group of six international mediators signed the Joint Comprehensive Plan of Action (JCPOA), ensuring the peaceful nature of Tehran's nuclear program in return for the gradual sanctions relief.