ANKARA (Reuters) - Turkish President Erdogan said on Sunday that Turkey would not succumb to  blackmail  by the United States in the trial of a Turkish bank executive being charged with evading U.S. sanctions on Iran. Already strained ties between NATO allies Ankara and Washington have deteriorated as Turkish-Iranian gold trader Reza Zarrab, who is cooperating with U.S. prosecutors, detailed in court a scheme to evade U.S. sanctions. Erdogan said Turkey s dealings were in line with the decisions of the United Nations, adding that they were not against Ankara s alliance with Washington.  What have we done, for example? We bought natural gas from a country we have an agreement with so our citizens wouldn t be cold in the winter. Like other countries, only the UN s decisions bind us, and Turkey followed them to the dot,  he told members of his ruling AK Party in the eastern province of Mus. Over three days of testimony, Zarrab has implicated top Turkish politicians, including Erdogan. Zarrab said on Thursday that when Erdogan was prime minister he had authorized a transaction to help Iran evade U.S. sanctions. Ankara has cast the testimony as an attempt to undermine Turkey and its economy, and has previously said it was a  clear plot  by the network of U.S.-based cleric Fethullah Gulen, who it alleges engineered last year s coup attempt.  This case is nothing more than the 17-25 December plot being carried across the ocean. Excuse us, but we will not succumb to this blackmail,  Erdogan said, referring to 2013 leaks about alleged government corruption which were blamed on his opponents. Although he has not yet responded to the courtroom claims, Erdogan has dismissed the case as a politically motivated attempt to bring down the Turkish government, led by Gulen. Turkey has repeatedly requested Gulen s extradition, but U.S. officials have said the courts require sufficient evidence before they can extradite the elderly cleric, who has denied any involvement in the coup. Gulen has lived in self-imposed exile in Pennsylvania since 1999.  