(Adds details from filings and on Iran nuclear agreement, byline)
By Jonathan Stempel
NEW YORK, April 4 (Reuters) - U.S. prosecutors on Wednesday asked a federal judge to sentence a Turkish banker convicted of helping Iran evade U.S. sanctions to about 20 years in prison, in a case that has strained diplomatic ties between the United States and Turkey.
Mehmet Hakan Atilla, 47, a former deputy general manager at Turkey's state-controlled Halkbank, had been found guilty by a federal jury in Manhattan in January.
Lawyers for Atilla did not immediately respond to requests for comment on the sentencing request.
Prosecutors said Atilla conspired with Turkish-Iranian gold trader Reza Zarrab and others from 2010 to 2015 in using fraudulent gold and food transactions to help Iran evade sanctions, which targeted the movement of oil proceeds and U.S. bank note and precious metals transactions.
"At a time when the United States and the community of nations were engaged in the momentous undertaking of depriving the Government of Iran of funding for its malign and deadly activities," including its alleged pursuit of nuclear weapons and support for terrorist groups, "Atilla was a key player in massively undermining those efforts," prosecutors said in a court filing.
Atilla is to be sentenced on April 11 by U.S. District Judge Richard Berman in Manhattan.
In 2015, the United States and other world powers agreed to lift sanctions on Iran in exchange for Tehran limiting its nuclear program.
U.S. President Donald Trump has threatened to pull out of the accord, which his predecessor Barack Obama supported, unless European signatories fixed its "terrible flaws" by May 12.
In a court filing last week, Atilla's lawyers urged leniency, saying the case did not involve "economic crimes" or a "crime of American disloyalty" by their client, a Turkish national, and that "no victims" suffered a financial loss.
They also said a lengthy sentence would keep Atilla, who has been detained for a year, more than 5,000 miles (8045 km) away from his wife and only son for too long.
Nine defendants have been charged in the case, but seven remain at large.
Zarrab pleaded guilty and became the star witness against Atilla, describing in several days of trial testimony a sprawling bribery scheme carried out with the blessing of President Tayyip Erdogan.
Erdogan has denounced the case, calling it a politically motivated attack on his government.
U.S. prosecutors said Atilla deserves a sentence "comparable" to the roughly 20 years imposed in analogous cases, and in any event longer than 15 years, eight months. They also said federal sentencing guidelines recommended a 105-year term. (Reporting by Jonathan Stempel in New York; editing by Grant McCool)