New York - A US jury will begin deliberations on Wednesday on whether to convict a Turkish banker of violating sanctions on Iran in a trial straining relations between Ankara and Washington and hinging on testimony from a flamboyant gold trader.US government prosecutors and defence lawyers delivered closing arguments in a Manhattan federal court on Tuesday, as the more than three-week trial captivating Turkey judders toward a close in New York.Deputy chief executive of Turkish lender Halkbank, Mehmet Hakan Atilla, is in the dock accused of violating sanctions against Iran, bribery and money laundering.But the most explosive aspect of the trial has been testimony from fellow accused, turned cooperating witness Reza Zarrab, who admitted being involved in the multi-billion-dollar gold-for-oil scheme to subvert US economic sanctions against Iran.His testimony implicated former Turkish ministers and even Turkish President Recep Tayyip Erdogan in the scheme, and identified 47-year-old Atilla as a key organiser."If you believe it then Mr Atilla is guilty," defence lawyer Victor Rocco told jurors on Tuesday. "But should you believe Mr Zarrab?"That is the question jurors will now have to decide.Zarrab, 34, was arrested by US authorities in March 2016 after jetting to Florida with his pop-star wife and child on a family holiday to Disney World. Shortly before the trial got underway, he cut an apparent plea bargain.'Liar'But in the words of Rocco, Zarrab is a "liar and a briber" who threw the book at Atilla only in the hope of himself avoiding a US prison sentence.His client, he insisted, was an "honest, hard working man", who was "not corrupt" and "has never been bribed".Atilla took the stand for two and a half days, denying that he had ever been in "any meeting where violating the sanctions were discussed".But US prosecutor Michael Lockard called him "a man of big and little lies" who lied about everything from his grasp of English to what he knew about sanctions.Atilla was Halkbank's "sanctions fixer", said fellow assistant US attorney Sidhardha Kamaraju, who alleged he took the risk of travelling to the United States in March 2017, after Zarrab's arrest, so certain was he of Turkish protection."He thought he was too big to jail," Kamaraju said.Any conviction risks further straining relations between Erdogan and US President Donald Trump, already damaged by rows over the Syria conflict and US prosecution of Turkish presidential bodyguards.It could also lead to US sanctions on the Turkish banking sector, beginning with Halkbank. The Turkish lender denies any suggestion that it violated US sanctions, saying it had "not been a party" to any "illegal" transaction.