Watch Martha Raddatz's interview with John Bolton in a one-hour special at 9 p.m. ET, Sunday, June 21 on ABC News.
In the interview, Bolton said of the December 2018 exchange, "it did feel like obstruction of justice to me."
SDNY prosecutors had been investigating the Turkish bank Halkbank for allegedly evading U.S. sanctions against Iran, a topic which Bolton said Turkey's President Recep Tayyip Erdogan raised with Trump by handing him a memo at the G20 Summit in Buenos Aires in December 2018.
Bolton alleged there were a number of conversations between the president and Erdogan of Turkey on the subject of Halkbank.
"What Erdogan wanted was basically a settlement that would take the pressure off Halkbank," Bolton said in his interview last week with Raddatz. "And the president said to Erdogan at one point, 'Look, those prosecutors in New York are Obama people. Wait till I get my people in and then we'll take care of this.'"
Bolton added, "And I thought to myself -- and I'm a Department of Justice alumnus myself. "I've never heard any president say anything like that. Ever." Bolton also served as United States Assistant Attorney General for President Ronald Reagan in his career.
SDNY, with backing from Attorney General Barr, returned an indictment against Halkbank in October of last year. The prosecution of Halkbank remains ongoing, though in February a U.S. appeals court agreed to a request from the bank to pause the case and proceedings have been stuck largely in limbo amid the ongoing COVID-19 crisis. The company has denied wrongdoing while resisting efforts by prosecutors to testify in a U.S. court.
Bolton in the interview acknowledged that the prosecution has continued despite the president's alleged conversation with Erdogan, but added that he found the episode "disturbing" as an example of the president's belief he could intervene in the justice system under the influence of a foreign leader.
"I don't think I know enough about all the circumstances, but I tell ya, it did feel like obstruction of justice to me," Bolton said. "The president has enormous power in the law enforcement area. The executive power is vested in the president."
"This idea that you give Erdogan and his family, who use Halkbank like a slush fund -- in exchange for, what, some hope down the road of some other kind of treatment for Trump or the country -- was very troubling."
Geoffrey Berman was appointed acting U.S. Attorney for the Southern District of New York by Trump's then Attorney General Jeffrey Sessions in January 2018 but has overseen the investigations of several Trump associates including Rudy Giuliani and Michael Cohen.
The Justice Department previously accused Bolton of "grossly" mischaracterizing a conversation he said he had with Barr, where he said Barr expressed concerns about Trump's alleged efforts to intervene in criminal cases, including the Halkbank case.
"There was no discussion of 'personal favors' or 'undue influence' on investigations, nor did Attorney General Barr state that the President's conversations with foreign leaders were improper," DOJ spokesperson Kerri Kupec said. "If this is truly what Mr. Bolton has written, then it seems he is attributing to Attorney General Barr his own current views -- views with which Attorney General Barr does not agree."