NEW YORK - An executive at Turkey's majority state-owned Halkbank took the witness stand in a New York courtroom on Friday and denied charges that he participated in a scheme to help Iran evade US sanctions.Mehmet Hakan Atilla, who has been on trial in federal court for three weeks, told jurors that he "never" conspired with fellow defendant, Turkish-Iranian gold trader Reza Zarrab, as US prosecutors have charged. Zarrab pleaded guilty and testified for the prosecution.US prosecutors have charged nine people with conspiring to help Iran evade sanctions through fraudulent gold and food transactions, although only Zarrab, 34, and Atilla, 47, have been arrested by US authorities.Responding to questions in court from one of his lawyers, Cathy Fleming, Atilla directly contradicted some of the evidence presented during the trial.Zarrab had told the jury that he had seen Atilla's superior call Atilla on an afternoon in April 2013 and order him to authorize an illicit transaction. Atilla testified that he was on a plane at the time.Atilla also said a recorded phone call played in court, purportedly between him and Zarrab, was actually between Zarrab and another Halkbank employee.Earlier this week, Atilla's lawyers asked US District Judge Richard Berman in Manhattan to order a mistrial following testimony from a former Turkish police officer, Huseyin Korkmaz, who said he had investigated Zarrab and Turkish government officials years earlier. They said Korkmaz's testimony of fleeing Turkey to avoid retribution unfairly associated Atilla with "cruel political violence."The judge, without the jury present, denied the request for a mistrial on Friday. He said Korkmaz had actually helped Atilla by testifying that Atilla was never caught on surveillance videos or found to take bribes in the investigation.The judge criticized the cross-examination of Korkmaz by Todd Harrison, one of Atilla's lawyers. Harrison on Thursday asked about possible links between Korkmaz and Fethullah Gulen, a US-based cleric blamed by the Turkish government for last year's failed coup.Berman said it was "unpersuasive and borderline unprofessional" to bring up what he called an "illogical foreign conspiracy theory" in court.The case has strained ties between the United States and Turkey. A spokesman for the Turkish government has called the case a "plot against Turkey."Both Zarrab and Korkmaz implicated Turkish officials, including President Recep Tayyip Erdogan, in their testimony.Attempts to reach a spokesman for Erdogan to comment on the testimony have been unsuccessful. Erdogan has previously dismissed the case as a politically inspired attempt to bring down his government.