ISTANBUL — Mehmet Hakan Atilla, a Turkish banker convicted of helping Iran evade US sanctions, resigned as head of Turkey’s Borsa Istanbul Stock Exchange, according to a statement released by the exchange Monday.

Atilla resigned “of his own accord,” according to the statement, and the decision was accepted by the board of directors Monday. Last week, Bloomberg reported Atilla was preparing to step down later this month, citing unnamed sources, though no motives have yet to be confirmed.

The move comes ahead of a New York trial of the Turkish state-owned Halkbank, expected to begin in May. The bank faces a fine of up to $20 billion for facilitating transactions that helped Iranian officials circumvent US sanctions in 2012 and 2013 for the nation’s nuclear program. As a former deputy executive of Halkbank, Atilla was convicted in 2018 of participating without profiting in the scheme and served a 28-month prison sentence in the United States.

After his release and return to Turkey in 2019, Atilla was appointed as CEO of the Borsa exchange by then-Finance Minister Berat Albayrak, who is also the son-in-law of Turkish President Recep Tayyip Erdogan. Some observers have suggested the resignation might be an attempt to restore strained US-Turkey relations before the Halkbank trial, though many remain puzzled by the development.