Turkey's Deputy Prime Minister Bekir Bozdag says the case in the US is aimed at harming economic relations between Turkey, Iran and Russia.
A US court case against Turkish-Iranian businessman Reza Zarrab is a "clear plot against Turkey" which lacks any legal basis, Turkish government spokesman Bekir Bozdag said on Monday.
The Zarrab case, who hearing was postponed until December 4 in the US, has complicated already strained relations between Washington and Ankara, both members of the NATO military alliance.
Turkish businessman Reza Zarrab, 34, has been in jail in the US pending trial.
He was detained in March 2016 on fraud and Iran sanctions-related charges.
"None of the evidence in this case is legal, you cannot use illegal documents as evidence," Bozdag told reporters after a cabinet meeting.
The former Deputy General Manager of Halkbank Mehmet Hakan Atilla is also detained in the US awaiting trial on the same charges as Zarrab.
US prosecutors have charged the Iranian-born Zarrab and his alleged co-conspirators of evading US sanctions.
While nine people have been criminally charged, only Zarrab and Atilla, are in US custody.
Both have pleaded not guilty.
"The fruit of the poisonous tree also becomes poison. Nothing that is contrary to the law can be used as evidence in any mechanism of justice. They are carrying out trials on the basis of fabricated documents," Bozdag added.
"Economic relations between Turkey and Iran complies with the domestic and international law."
Turkey investigates US judiciary over FETO links
Turkey also has launched a probe into two American lawyers, including a former attorney and an incumbent attorney in the US who are currently involved in a case against Turkish citizens in New York.
The Public Prosecutor's Office in Istanbul on Saturday accused former US attorney Preet Bharara and current US attorney Joon H Kim for the southern district of New York of using information and documents from previous investigations in Turkey for an ongoing case in the US.
Bharara, who had launched a probe against Zarrab, was fired on March 11.
Joon H Kim is the acting United States Attorney for the southern district of New York.
Ankara holds the US-based leader Fetullah Gulen and his network (FETO) responsible for orchestrating the coup attempt on July 15, 2016, which left at least 250 people dead and around 2,200 injured.
Gulen, who has lived in self-imposed exile in the US since 1999, denies any involvement.