Hakan Atilla, the former Turkish banker who served a prison sentence in the US for helping Iran evade sanctions, has taken leave as CEO of Borsa Istanbul until shareholders meet later this month, prompting market speculation that he may be replaced.

Bloomberg reported that Atilla will step down at the shareholders’ meeting, citing unnamed sources.

Atilla was named head of Borsa Istanbul, owned by the state’s Turkish Wealth Fund (TWF, or TVF), in October 2019 after the US deported him following a 28-month prison sentence. At the time, the move was widely seen as made by the Erdogan administration as part of its campaign to attack the credibility of New York prosecutions aimed at the sanctions-busting allegedly facilitated by Turkish state bank Halkbank. If Atilla resigns his position at the stock exchange, it may prompt speculation that the move is designed to send another signal to the Biden administration in the US that Turkey is ready to strike compromises on certain disagreements between Ankara and Washington.

“He [Atilla] has gone on leave at his own request, and we expect that he will remain on leave until the general assembly,” a spokesman for Borsa Istanbul was cited as saying by the Financial Times. Atilla has not resigned, and a decision about his future at the bourse may come at the annual meeting on March 26, he added.

Atilla was convicted of bank fraud and conspiracy for helping Iran conduct an illicit oil trade through transactions at Halkbank. He was deputy CEO at Halkbank until his arrest in 2017 in the US.

Turkey is bracing for another trial, expected to begin in May, in New York against Halkbank on charges of fraud, money laundering and sanctions offences. US prosecutors allege Iran channeled around $20bn in oil revenue through the bank to dodge sanctions for its nuclear programme in 2012 and 2013.

A large fine and other punitive actions against Halkbank could cause reverberations that hit Turkey’s banking system.

President Recep Tayyip Erdogan has lobbied the US government to dismiss the case against Halkbank.

Borsa Istanbul plans an initial public offering next year. The government controls 90% of the exchange company. The European Bank for Reconstruction and Development (EBRD) sold its 10% stake to the TWF after opposing Atilla’s appointment. The Qatar Investment Authority last year purchased a 10% stake in the bourse for $200m.